What Cartridge Other Than The 223 Rem Are You Looking To Build In An Ar15


The Grumpy Grease Monkey mechanical engineer.
Staff member
what cartridge other than the 223 rem/5.56mm
are you looking to build in an ar15 basic rifle?
now theres several dozen or more popular choices,
choices like
the 10mm auto that uses glock mags
or cartridges that add a bit more power.
pistol cartridge carbines are always a compromise in lower range and power.
every choice made is understood to be a compromise in some area
generally the original 223 rem case lacks the ideal increased ,powder capacity,
to maintain high velocity with bullets over about 6.5 mm, but if your willing to accept lower velocity,
the cartridges using the 223 rem case, like the 350 legend have potential for CQB carbines





Im trying to decide on a cartridge to use in a AR15 based ,rifle build
this will have a 16"-20 HEAVY STAINLESS BARREL
heres the basic requirements as far as I see them,
the rifle must retain use of, and work, and ideally have been made with the original mil spec magazines
the use of as many original plentiful mil speck parts as possible is a big plus,
it must be at least 24 caliber but not more than 30-35 caliber
the cartridge must be able to provide more impact power/penetration, with the correctly
selected bullets, than a 223 rem has at 400 yards
Valkyrie has
a bit more velocity than a 223, and its designed to work with heavier 70-77 grain bullets
The 6×45mm is a rimless, bottlenecked cartridge based on the . 223 Remington or 5.56 NATO cartridge necked up to . 243 (6mm). The cartridge is also known as the 6mm-223 Remington or 6mm/223.
(this seems like a potential no brain improvement)

25/45 sharps


6.5mm Grendel

personally, after looking over most of the AR15 caliber conversion options I think the BEST BALANCE in power/velocity/and penetration on game of for personal defensive use is found with a 18"-20" barrel AR15 in 6,8 SPC
6.8 SPC, and 6.5mm Grendel , are options that provide you with, a noticeable improvement in close range lethality with only a minimal loss in cartridge capacity, the 6.5 has a bit more effective reach, but the 6.8 would be my choice in CQB,
both potentially provide a big improvement in lethality over the 223 in an ar 15 platform,
the 6.8mm and 6.5mm
Grendel are both considerable improvements over a more common 223 rem. in cartridge choice for close quarters battle/ personal defensive use, as both retain considerably more lethality out past 300 yards than a 223 rem.
and both I consider improvements over the 7.62/39 AK cartridge.
that allows use of most of the original ar15 components other than, the mandatory upgrade too a new barrel, and new magazines
as the AR platform is just consistently more accurate
Ive talked with several guys I know who hunt with AR15/6.8 spc carbines, they all say the results they see,
duplicate the better 30/30 rifles they have used, thus improving the basic AR15 into a very effective closer range combat arm,
with a noticeable improvement in lethality, over the 223 rem, out to maybe 300 yards.
110-130 grain bullets are preferred with the 115-120 the more popular weights
300 black-out,

you might want to think of the 300 black-out as
a cartridge designed for suppressor use

these plated cast, 220 grain, bullets are designed to use with a suppressor,
in a 300 black-out, cartridge in an AR15 carbine ,with a suppressor,
typically a 10"-16" barrel to keep the over all length reasonable.
they cost only about 20 cents each keep the velocity below 1250-1300 fps.
faster powders preferred,

the 300 black-out , loaded with the 220 grain bullet,
has easily more than double the typical 9mm carbines power at 100 yards:D


10.5 grains of IMR 4198
is a common well liked load in a
suppressed 300 black-out with a 220 grain bullet

and use a 7:1-to-9:1 twist rate barrel to maximize accuracy and not have
suppressor issues,
remember you want to have heavy and accurate projectiles leave the suppressor,
be below the sound barrier,
this 220 grain plated bullet in a 300 black out,
far exceeds the typical 9mm sub machine guns power ,
accuracy, range and penetration,


with a 220 grain bullet at 1000 fps, making it far more lethal than a 9mm submachine gun cartridge,
at ranges out to about 150 yards with a suppressor in use,
and if swapping to a non-suppressor use,
and about 130-150 grain ammo far more lethal than a 223 rem,
out to about 350 -400 yards

350 legend, (this is fairly new but has the potential to be an excellent hunting and self defense cartridge out to at least 250 yards with the correct bullet selected.)
a well documented and lethal 35 caliber/9mm bore size cartridge ,
designed to allow use of a ar 15 platform in areas that only allow strait wall cartridges for deer hunting,
best used at under 150-200 yards on deer and hogs, but certainly lethal as a military cartridge out to 250 plus yards

50 beawulf
458 socom,
are popular with those who hunt medium / deer/hogs
many require special magazines along with new barrels, bolt
the ones I high lighted/(BOLD)
seem to be the most popular in the group of guys I hang out with.
any of the four bold choices are better than the 223 rem for hunting,
as any of the four provide more impact energy,
heavier bullets and deeper penetration,
but it really helps if you hand load as ammo cost can be much higher
and all four cartridges listed in bold work well in 16" or better yet 20" barrel lengths







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I've been really thinking about that subject I bought some stripped lowers about 10 years ago and I'm down to my last one and been thinking about building a more top of the line different caliber I have them in 223/556 an AK 7.62x39 and an AR 10 308 so I have all the real needs filled what would you build in this situation my only real want is accuracy and a different caliber I'm just not sure what I want to do yet
Along with accuracy I want a 20+ inch barrel and big enough to hunt Pa. deer and I think anything bigger than a 223 fits the bill








BTW if your looking for a good self defense and hunting cartridge choice in the AR15 rifle the 6.8,mm SPC cartridge is a very useful blend of performance characteristics, you only loose a little in flat trajectory , and only a couple cartridges in mag capacity, but gain very noticeably in performance on target
the 6.8 spc seems to feed and function much better (flawlessly so far) than the 6.5 grendal in the two rifles I tested friends own,
and watching hit steel targets its obviously far superior to the 223 in impact energy
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350 Legend vs 300 Blackout: A Clinic on Purpose-Driven Rifle Cartridges

The 350 Legend and 300 AAC Blackout are two centerfire rifle cartridges that are often employed by deer hunters to bag that trophy buck or stock their freezers full of venison every fall.

Although both cartridges are excellent options for taking down whitetail or feral hogs, this comparison really comes down to understanding the purpose that each cartridge was developed for.

The 350 Legend was developed by Winchester specifically as a hunting round, while the 300 Blackout was developed for US Special Forces to be fired with a suppressor from the AR-15 platform.

Even though the 300 Blackout was designed for urban combat, it has been accepted by the hunting community as an effective dispatcher of whitetail deer and is used by many shooters every fall.
In this article, we will take a deep dive into the 350 Legend vs 300 Blackout cartridge debate and analyze the advantages and disadvantages of each, so you can make a more informed decision on your new hunting rifle.
What is the Difference Between 350 Legend and 300 Blackout?

The primary difference between the 350 Legend and 300 Blackout is the bullet diameter and case design for each cartridge. The 350 Legend fires a 0.355” diameter bullet from a straight-walled cartridge while the 300 Blackout fires a 0.308” diameter bullet from a bottleneck cartridge.
Cartridge Specs

When comparing two rifle cartridges, it’s a good idea to analyze the cartridge specs to gain more knowledge of each.

The first major difference to discuss is the design on the cartridge case itself, as the 300 Blackout is a bottleneck case while the 350 Legend uses a straight-walled case. A bottleneck case is typically more efficient, as it allows for a higher case capacity since the base of the bullet resides in the neck of the cartridge instead of the body. However, the 350 Legend was specifically designed as a straight-walled cartridge to meet the rigid DNR requirements of states like Ohio, Michigan, Indian, and Pennsylvania that require such cases for deer hunting.

The next major difference is the bullet diameter that each hunting cartridge fires. The 300 Blackout fires the popular 30 caliber bullet, or 0.308” bullet diameter. For the 350 Legend, Winchester uses a bit of marketing magic in how it describes the projectiles its cartridge fires.

You’ll notice that the bullet diameter for 350 Legend is listed as 0.357”-0.003”, which is odd since caliber is usually just a single diameter measurement. This strange nomenclature is due to specific state requirements that rifle cartridges used for deer hunting must fire a minimum of a 0.357” diameter bullet.

Winchester lists the 350 Legend as firing a 0.357” caliber bullet on their website, however all reloading data recommends the use of 0.355” bullets (otherwise known as 9mm). Although the 350 Legend is capable of firing a 0.357” diameter bullet, it is more frequently loaded with the slightly thinner 0.355” bullet. This strange caliber designation allows for some wiggle room with bullet selection while still maintaining legality in states that have the 0.357” bullet diameter requirement.

One similarity between the 350 Legend and the 300 AAC Blackout is that they have the same rim diameter (not listed) as the 223 Remington, 0.378”. This means that integration of the 350 Legend into the AR-15 platform would only require a barrel change.

Although the overall length measurements of the 350 Legend vs 300 Blackout are nearly identical, the case capacity is quite different as the 350 Legend has more space due to it being a longer and wider case overall. The 350 Legend has a case capacity of 36.5 gr compared to 26.5 gr for 300 Blackout.

The added case capacity allows the 350 Legend to fire a heavier bullet, but how does that affect recoil?


One of the main selling points that Winchester likes to point out about their deer hunting darling cartridge, 350 Legend, is that it has about 63% less recoil than the 450 Bushmaster, and 60% deeper penetration than the 223 Rem. Those are impressive numbers, but how does it stack up against the 300 Blackout?

On average over several supersonic loadings, the 300 Blackout will have 6 ft-lbs of felt recoil while the 350 Legend will have around 8.5 ft-lbs of felt recoil.

Although the 350 Legend does technically have more felt recoil than the 300 BLK, neither is oppressive to shoot and marksmen would describe both cartridges as having low recoil.

Muzzle Velocity and Kinetic Energy

Muzzle velocity, measured in feet per second (fps) is the speed at which the bullet leaves the barrel of the firearm. Generally, a longer barrel length will generate a higher muzzle velocity because it allows for a more complete powder burn.

Muzzle energy is measured in foot-pounds (ft-lbs) and is a measurement of how much force a bullet delivers to its target at a given range.

The 150 gr Winchester Deer Season XP loadings for both calibers will be considered for this comparison. For this load, the 350 Legend will have a muzzle velocity of 2,325 fps and muzzle energy of 1,800 ft-lbs according to Winchester’s data. In comparison, the same load in 300 Blackout will have a muzzle velocity of 1,900 fps and muzzle energy of 1,200 ft-lbs.

The 350 Legend is clearly superior in terms of muzzle velocity and energy.


Trajectory is how we quantify a bullet’s flight path as it travels downrange measured in inches of bullet drop.

Obviously, a flatter shooting cartridge is preferred for shooting longer ranges, as a shooter will require fewer adjustments to their optics to compensate for bullet drop. Having a flatter trajectory also means that a cartridge will be more forgiving of ranging mistakes.

As the 350 Legend has a higher muzzle velocity, it will generally have a flatter trajectory.

Using the same 150 gr Winchester Deer Season XP loadings, we see that at 200 yards the 350 Legend has experienced -7.6” of bullet drop compared to -9” for the 300 Blackout.

This may not be a huge difference at this short range, but the gap between the two becomes more exacerbated at longer ranges.

This difference in trajectory coincides with the listed maximum effective range for both rifle cartridges. Winchester states that the 350 Legend is effective on whitetail out to 250 yards, where the 300 Blackout has a maximum hunting effective range around 175 yards on a good day.

Ballistic Coefficient

Ballistic coefficient (BC) is a measure of how well a bullet resists wind drift and air resistance. Put another way, it’s a numeric representation of how aerodynamic a bullet is. A high BC is preferred as this means the bullet will buck the wind easier.

Generally, heavy bullets will have a higher BC as it takes more force to disrupt the flight of a heavier bullet than a lighter one. Ballistic coefficient varies from bullet to bullet based on design, weight, and other factors that are beyond the scope of this article.

Ballistic coefficient is one category where the 300 Blackout reigns supreme.

With its more aerodynamic Spitzer bullet design, the 300 Blackout defeats the 350 Legend by a wide margin. Sticking with our same Deer Season XP loads, the 350 Legend has a BC of 0.223 compared to 0.392 for 300 AAC Blackout.

That’s a pretty big difference and showcases how bullet design plays a critical role in Ballistic Coefficient.

Sectional Density

Sectional Density (SD) is the measure of how well a bullet penetrates a target. This is extremely important when hunting big and medium sized game, as you need a bullet that can punch through thick hide, bone, and sinew.

Sectional density is calculated by comparing the bullet weight and the bullet diameter. The higher the SD the deeper the bullet will penetrate into the target. This is a simplified view of penetration as there are other factors to consider, such as bullet expansion and velocity.

Bullet jacket design also plays a part in penetration, as a bullet designed to expand like a soft point (SP), ballistic tip, or jacketed hollow point (JHP) will naturally penetrate less than a full metal jacket (FMJ).

At the time of writing, Winchester has not published sectional density data for their 350 Legend cartridge on their website. Winchester makes the claim that the 350 Legend penetrates around 10% less than 30-30 Win.

Although Winchester has not published their SD calculations, Hornady has recently started producing their own loads for 350 Legend and has SD data available. Unfortunately there are no Hornady loads that are the same bullet weight for both cartridges, so this won’t be a perfect apples-to-apples comparison.

The Hornady 135 gr FTX Custom 300 Blackout round has a sectional density of 0.203 compared to a 165 gr FTX Custom 350 Legend with a SD of 0.187. Although the bullet weights for these two cartridges is slightly different, it does suggest that the 300 Blackout will have a higher sectional density and therefore penetrate deeper into a big game animal.


The increased effective range and kinetic energy provided by the 350 Legend make it the clear choice for hunting purposes. And this shouldn’t come as a surprise to many, as the 350 Legend was specifically designed as a deer hunting round.

This is not to say that the 300 Blackout is an ineffective hunting cartridge. On the contrary it is extremely effective at close range or when faster follow-up shots are needed, like when hunting feral hogs.

However, deer hunters typically opt for a single shot or bolt-action rifles as semi-automatic fire is not needed for whitetail (and sometimes prohibited by law). This nullifies much of the advantage of the 300 BLK and its seamless integration with the AR-15 platform.

The 300 Blackout and 350 Legend are both capable of firing subsonic ammo, however it is not advisable to use either of these subsonic rounds for hunting purposes. Subsonic offerings for both rounds lack the needed kinetic energy and expansion needed for ethical hunting, therefore it is NOT recommended to used subsonic ammo for hunting big game.

For varmint hunting, the low recoil of the 300 Blackout gives it a slight advantage over the 350 Legend. Furthermore, the 300 Blackout has more lightweight bullet options that are ideal for smaller varmints like the 110 gr Hornady V-MAX. However, for anything smaller than a coyote, you would be better served with a 223 Rem or 22-250 as these rounds are designed for this purpose.

There’s nothing to say you can’t use a 350 Legend or 300 Blackout for a groundhog or woodchuck, but it’s a bit overkill if you ask me. For anything smaller than a coyote, you would be better served with a 223 Rem or 22-250 as these rounds are designed for this purpose.

Suppressor Integration

One of the key attributes of the 300 AAC Blackout is its ability to be effectively suppressed in a short barrel AR-15 (or M4 carbine for our military).

In close quarters battle (CQB) like our soldiers experienced in the urban setting of Iraq, having a maneuverable rifle with a short barrel and a suppressor to reduce the rifle report is critical for maintaining situational awareness and communication during a firefight indoors.

As sound will echo off interior walls, a rifle fired indoors will be considerably louder than what is experienced shooting outdoors, necessitating the use of suppressor.

Suppressors work by reducing the sound of the gunpowder igniting during the firing sequence. However, the sonic crack of the bullet breaking the sound barrier cannot be reduced by a suppressor.

Most rifle cartridges are fired at supersonic speeds, meaning faster than 1125 fps.

Both the 350 Legend and 300 Blackout have subsonic factory loads available for use with a suppressor.

The 300 Blackout has a slight advantage over the 350 Legend for suppressor use since the 300 Blackout is designed to experience a full powder burin in only 9 inches of barrel length. This makes for a very lightweight, compact carbine package that is extremely easy to suppress.

Home Defense

As the 300 Blackout was designed for CQB applications, it is clearly the better option for self-defense.

This is not to say that a 350 Legend cannot be utilized in a home defense application, it will serve you admirably should you need to bring it to bear against an attacker. However, the inability of the 350 Legend to fit into standard AR-15 mags is a clear mark against the cartridge.

Furthermore, the 300 Blackout has less recoil than the 350 Legend, meaning that follow-up shots will be quicker when firing a 300 BLK rifle. Full 30-round magazine capacity and low recoil make the 300 Blackout the better choice for self-defense.

Ammo and Rifle Cost/Availability

As the 350 Legend is a relatively new cartridge on the market, there are fewer ammo options available compared to 300 Blackout. Winchester, Hornady, and Federal are the primary suppliers of 350 Legend ammo, whereas almost every manufacturer has a 300 Blackout ammo option for sale.

Although the 300 Blackout has more ammo options available, the cost per round is virtually identical for 300 Blackout and 350 Legend. Inexpensive full metal jacket (fmj) practice ammo typically runs around $1/round while premium hunting ammo goes for about $2/round.

In terms of rifle availability, the 300 Blackout is the clear choice as any standard AR-15 can be converted to 300 BLK with a simple barrel change. Furthermore, many manufacturers offer 300 Blackout AR-15 rifles straight from the factory, so no conversion is needed.

Converting an AR-15 to 350 Legend is not difficult as the bolt used for 223 Remington/5.56 NATO can be used, however new magazines specific for 350 Legend have to be acquired. This need for special magazines is one of the reasons that other calibers like the 6.5 Grendel or 6.8 SPC have only seen mild popularity in the AR shooting community.

In terms of bolt action rifles, manufactures like Ruger and Savage both have options for the 300 Blackout and 350 Legend. The Ruger American Ranch offers an affordable, magazine-fed, lightweight bolt action rifle in both calibers that is ideal for deer hunting.


Creating your own hand loads for both 350 Legend and 300 Blackout can be extremely rewarding and a cost-saving measure that allows you to practice more with your rifles.

In terms of component availability, the 300 Blackout has the edge as it fires the extremely common and popular 30 caliber bullet. This means that you can easily stockpile components for 308 Winchester, 30-06 Springfield, and 300 Win Mag as they all fire the same bullet diameter.

Furthermore, 300 Blackout brass is considerably easier and less expensive to acquire than 350 Legend. In fact, a savvy reloader can form their own 300 Blackout brass from 223 Remington cases with the proper dies and some patience.

On the other hand, 0.355” diameter rifle bullets are less commonly used. Although 0.355” is the same diameter as 9mm pistol bullets, handgun bullets and rifle bullets are designed differently. This means that there will be fewer bullet options available for 350 Legend and you’ll have to purchase them specifically for that cartridge.

In terms of brass, you’ll have to either save your factory 350 Legend cases or purchase factory new as the 350 Legend is a unique case design.

Despite these drawbacks, many hunters love making their own hand loads for 350 Legend, as this allows them to tailor their ammo to their specific rifle.

However, reloading for 300 Blackout offers more benefits with the cross-compatibility with other 30 caliber cartridges as you can save money by purchasing projectiles for both in bulk.

A Brief History of 350 Legend

The 350 Legend is a rifle cartridge that was developed to fill a particular role in the deer hunting community.

Developed by Winchester Repeating Arms and accepted by SAAMI in 2019, the 350 Legend is a rimless, centerfire, straight-walled cartridge that was designed to meet the needs of hunters in states like Michigan, Indiana, Ohio, Illinois, and Pennsylvania. Hunters in these states are required, by law, to use straight-walled cartridges for deer hunting and have previously been restricted to heavier cartridges like the 450 Bushmaster or 444 Marlin.

Winchester sought to produce a low recoil, heavy hitting cartridge that met the overall length and bullet diameter requirements of these states, and the 350 Legend was the result.

Capable of firing 150 grain 0.355” projectiles at 2,325 fps and with 1,800 ft-lbs of kinetic energy, the 350 Legend is a potent cartridge capable of harvesting a whitetail at 250 yards.

The cartridge was revealed to the shooting community at 2019 SHOT Show and was initially offered in Winchester’s XPR bolt action rifles. Since its debut, other rifle manufactures like Ruger and Savage have seen the potential of the cartridge and chambered it in their own rifles.

As the 350 Legend shares the same rim diameter as the 223 Rem, the 350 can be integrated into the AR-15 platform with a barrel change. However, the 350 Legend is not compatible with standard AR-15 magazines, so 350 Legend AR mags are also needed.

Capable of firing bullet weights ranging between 125 and 280 grains, the 350 Legend offers shooters the flexibility to hunt small to big game with the same rifle.

A Brief History of 300 Blackout

The development of the 300 AAC Blackout (designated 300 BLK by SAAMI) rifle cartridge began in 2010 when Robert Silvers of the Advanced Armament Corporation (which was later acquired by Remington) was approached by a member of the US Military “dark ops” community.

Some special forces units were unhappy with the stopping power that the 5.56 NATO and the 9mm (used in several SMGs) offered during close range engagements and he wanted something that had more “oomph”. Something along the lines of the 7.62x39mm.

However, there were some other requirements that this customer required as well:
  1. The rounds needed to fit into STANAG standard AR-pattern mags and maintain their 30-round capacity
  2. The cartridge case head must be the same as 5.56mm NATO so a bolt change was not needed
  3. It had to shoot 30 caliber projectiles and mimic the terminal performance of the 7.62x39
  4. The new rifle cartridge needed to be compatible with short barrel rifles (SBR, barrels under 16”) and be completely functional with a suppressor/silencer
  5. Supersonic and subsonic ammo needed to be available and functional
Integrating new calibers into the AR-15 platform is nothing new to the shooting community. The 6.8 Remington Special Purpose Cartridge (SPC) and 6.5 Grendel are two examples that were mildly successful; however, they both required a new bolt and did not maintain the 30-round capacity requirement.

Simply modifying a M4 to fire 7.62x39mm was not an option either as the severe case taper causes multiple chambering issues using standard M4 mags. This is why you see such extreme curvature in AK-47 magazines.

A new cartridge had to be developed and the 300 Whisper, pioneered by JD Jones, was selected as the parent case. Since the 300 Whisper was a wildcat cartridge, and therefore could not simply be adopted for military use as it was not SAAMI standardized.

The new round was called the 300 AAC Blackout (300 BLK or 300 Blackout) and was approved by SAAMI on January 17, 2011.

300 BLK ammo can be broken down into two different bullet weights, 200+ grain subsonic and 110 to 125 grain supersonic.

Supersonic ammo, typically firing a 125 grain bullet, will have a muzzle velocity of approximately 2250 fps and have a muzzle energy of around 1404 ft-lbs. Industry standards list the effective range of the supersonic 125 grain bullet loadings to be 500 yards.

In contrast, subsonic loads will fire a 220 grain bullet and have a muzzle velocity of around 1000 fps and a muzzle energy of 488 ft-lbs with an effective range of 200 yards.

These two popular loadings really illustrate the versatility of 300 BLK ammo. With a simple magazine change, a shooter can switch from supersonic ammunition and long-range engagements to subsonic ammunition for short range combat.

Furthermore, the 300 BLK was designed specifically to experience a full powder burn when being fired in a 9” short barrel rifle (SBR), preferably with a suppressor/silencer.

If you’d like to learn more about how the 300 BLK compares to other calibers, check out these articles below:
Final Shots: 350 Legend vs 300 Blackout

The 300 AAC Blackout and 350 Legend are two rifle cartridges that were developed to fill a specific niche in the shooting community.

The 350 Legend was developed to offer hunters in the Midwest a low recoil, long range hunting round that met the cartridge requirements of some states like Ohio and Michigan. It is effective on whitetail out to 250 yards and can be utilized against feral hogs and coyotes as well.

The 300 AAC Blackout was developed with the AR-15 platform in mind for close quarters battle. With low recoil and the ability to maintain full capacity in 30-round AR magazines, the 300 Blackout makes for a potent carbine capable of firing both supersonic and subsonic rounds. The decision between 300 Blackout vs 350 Legend greatly depends on your intended use for the cartridge.

If you plan to go deer hunting in a state that requires the use of straight-walled cartridges, then the 350 Legend is clearly the obvious choice. However, if you are looking for a cartridge that easily integrates into the AR-15 carbine for use with or without a suppressor, then 300 Blackout makes the most sense.

However, if you live in a state that does not have straight-walled cartridge requirements, there is little benefit to selecting a 350 Legend, as something like a 308 Win or 30-06 Springfield offers you greater long range capability and excellent terminal ballistics without sacrificing the efficiency of a bottleneck cartridge.

The bottom line is that the 350 Legend was developed to fill a specific need for deer hunters in states with restrictive cartridge requirements. Although the 350 Legend does have some utility for other applications and is ballistically superior to the 300 Blackout, it is unlikely to see the widespread success of the 300 BLK due to the need for special 350 Legend magazines in an AR-15.

Selecting the best cartridge for your needs depends on your state requirements and needs as a shooter. Regardless of which one you choose, make sure to get all of your ammo here at Ammo.com and I’ll see you out on the range!

350 Legend vs 300 Blackout: A Clinic on Purpose-Driven Rifle Cartridges originally appeared on Ammo.com
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I like my 308 still easy to load and get stuff for still love to shoot my AK though there is just something about it now my AR pistol is in my opinion worthless
I have one lower left that I'm going to build something different caliber wise moving away from 223 in these times will be tough I'm thinking of a 20 inch heavy bbl with all better internals and a better trigger for sure

watching the difference between a 223 vs a 6.8 spc on 200 yard steel targets there's a huge increase in impact energy with the 6.8 spc
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I have several 223/556 rifles and a pistol and a 308 and an AK 7.62 x 39 my next toy I think will be a longer barrel 223/556 20 inch or longer right now I'm looking into that because I have an extra lower and before I can't get what I want I would like a better/longer shooter
a 6.5 Grendel or 6mm arc with a 24" barrel extends the range considerably longer than any 223

24-inch AR15 Varmint Upper Half, 6.5 Sporter caliber, 1-9 twist$450.00
Stainless Steel Stainless steel, 5/8x24 threaded muzzle: +$50.00
Aluminum free float, knurled Alum. free float, knurled, swivel stud: +$10.00 Alum. free float, fluted: +$10.00 Alum. free float, fluted, swivel stud: +$20.00 Alum. free float, fluted & knurled: +$10.00 Alum. free float, fluted & knurled, swivel stud: +$20.00 YHM free float 4 rail: +$140.00 YHM free float 4 rail with end cap: +$156.00 YHM smooth free float: +$140.00 MI 2 piece free float 4 rail: +$230.00 Young vented free float 4 rail: +$155.00
None Selected Removable carry handle, std aperture: +$75.00 Removable carry handle, NM aperture: +$75.00 Flip rear sight, 4 aperture: +$65.00 YHM flip rear sight: +$75.00 MI flip rear sight: +$85.00 MI low pro flip rear sight: +$85.00 PRi flip rear sight: +$120.00
None Selected Removable front sight, gas block mount: +$45.00 YHM flip front sight, gas block mount: +$65.00 MI flip front sight, gas block mount: +$75.00 YHM flip front sight, forearm mount: +$65.00 MI flip front sight, forearm mount: +$75.00
None Selected Bolt carrier group & std charging handle: +$140.00 Bolt carrier group & ext latch chrg handle: +$143.00 Bolt carrier group & Wook ambi chrg handle: +$146.00 Bolt carrier group & tact latch chrg handle: +$149.00 Bolt carrier group & Badger ext latch chrg handle: +$154.00 Black bolt & chrome carrier, std charging handle: +$205.00 Black bolt & chrome carrier, ext latch chrg handle: +$208.00 Black bolt & chrome carrier, Wook ambi chrg handle: +$211.00 Black bolt & chrome carrier, tact latch chrg handle: +$214.00 Black bolt/chrome carrier, Badger ext latch chrg hndle: +$219.00
None Selected Versa-Pod: +$75.00 Versa-Pod with rail adapter: +$120.00 Harris swivel model: +$97.00 Harris swivel model with rail adapter: +$125.00
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I have so much 223/556 stuff like Mags. Ammo and different parts I did consider a 6.5 Creedmoor because I have one of them and a good start on ammo I've got to look at what I would need different besides the gun and I'm pretty sure the mags need an upgrade too
youll need only the full 6.5 upper and the matching mags, you can use a standard lower

6mm ARC vs 6.5 Grendel: Which AR-15 Round Is Best?

The 6mm ARC vs 6.5 Grendel is worthy of debate since both cartridges have the same parent cartridge.

Both were designed for the AR-15 platform for similar reasons, so which one does the job the best?

Honestly, it boils down to your intended purpose.

6.5 Grendel vs. 6mm ARC

These two rounds are incredibly similar, so does it matter which one you choose?

We say yes!

However, each caliber has its purpose, so we will break down which caliber is best overall, but we will also give you the circumstances when one is more beneficial than the other.

Cartridge Specs

The 6mm ARC and the 6.5 Grendel originate from the .220 Russian, so there is very little difference.

At a glance, experienced shooters will have difficulty initially telling the rounds apart.

The bullet diameters differ by only 0.021 inches, with the 6.5 Grendel being 0.264 inches while the 6mm ARC is 0.243 inches.

The rim diameter is even closer with only 0.001 inches difference—the 6.5 Grendel is 0.44 inches in diameter, whereas the 6mm ARC is 0.441 inches in diameter.

The 6mm ARC case is slightly shorter at 1.49 inches compared to the 1.52 inches of the 6.5 Grendel case.

The 6.5 Grendel has a broader range of bullet weights, ranging from 90 grains to 130 grains. In contrast, the 6mm ARC is offered in 103gr to 108gr.

The overall length of the rounds is the same at 2.26 inches.


From looking at the rounds, you could guess they have very similar recoil.

Felt recoil depends on many factors, including the gun's weight, bullet weight, and shooter.

Neither round is known for high felt recoil, but the 6mm ARC doesn't pack as much punch as the 6.5 Grendel, which has 9-foot-pounds of recoil due to the lower case capacity.

This is because it holds slightly less powder and fires smaller projectiles.

The 6mm ARC has a slight advantage for recoil and is an excellent choice to introduce individuals to firearms apprehensive of guns because of recoil concerns.


The trajectory is the bullet's path to the target.

As shooters, we prefer a flat-shooting round over ammunition that requires us to adjust for bullet drop.

That's why 6mm bullets are so popular amongst medium-range to long-range shooters. They're known to be flat-shooting bullets.

The 6mm ARC is a more aerodynamic bullet than the 6.5 Grendel. At 400 yards, it has an average bullet drop of 22.2 inches.

The bullet drop for the 6.5 Grendel is slightly greater because it's a larger bullet. However, 25.3 inches of drop at 400yds is by no means terrible.

Therefore, the 6mm ARC has a flatter trajectory by 3.1" at 400yds.

The bullet drop difference will be exponentially more significant as we extend the distance. However, both rounds are excellent long-range rounds.

By a narrow margin, the winner is the 6mm ARC.


Accuracy is defined as how close the bullet hits the target compared to where the shooter aims.

While the bullet does affect accuracy, it also largely depends on the shooter, rifle, barrel length, and optics.

The 6mm ARC and 6.5 Grendel calibers are so similar that I seriously doubt you'll see a difference in accuracy if you're using comparable rounds, rifles, and optics, meaning the same brand of powder, guns, and optics, similar bullet weights, and projectile types.

This category is a tie.

Since it will vary depending on the shooter, some people are more accurate with a lighter recoil firearm, while others aren't as bothered by the recoil and can be as accurate with both.

Ballistic Coefficient

The ballistic coefficient (BC) measures how well a bullet resists wind drift and air resistance.

Put another way; it’s a numerical representation of the aerodynamics of the bullet.

A high BC is preferred since it means the bullet will resist the wind more.

Generally, a heavier grain bullet will have a higher ballistic coefficient as it takes greater force to disrupt a heavier bullet than a lighter projectile.

The ballistic coefficient varies from bullet to bullet based on design (aerodynamics), weight, and other factors.

We would assume the 6.5 Grendel has a higher BC since it tends to have heavier bullets; however, the 6mm ARC typically has a higher ballistic coefficient because of its greater velocity and more aerodynamic bullet.

A 123gr 6.5 Grendel hunting cartridge has a BC of .510, while the factory ammunition 103gr 6mm ARC hunting cartridge has a BC of .512.

If we increase the weight of the 6mm ARC to 108gr eld match, the BC will increase to .536, while the BC will lower to .506 when we switch to a 123gr 6.5 Grendel match cartridge.

The winner is clear; the more aerodynamic 6mm ARC has a higher ballistic coefficient despite having lighter bullets.

Stopping Power/Sectional Density

Stopping power can be spoken of in terms of Sectional Density (SD), the measure of bullet penetration.

Stopping power is crucial when hunting big-game and medium-sized game since you'll need a bullet that can punch through thick hide, bone, and sinew to make a quick ethical harvest.

Sectional density is calculated by comparing the bullet weight and the bullet diameter.

The higher the SD, the deeper the bullet will penetrate the target.

This is a simplified view of penetration as there are other factors to consider, such as bullet expansion and velocity.

For this comparison to truly be accurate, we should use bullets that weigh the same. We can't, but we have the information that will give you a fair idea.

A 6.5 Grendel 123 gr Hornady hunting round has a sectional density of .252, whereas a 6mm ARC 103 gr hunting round has an SD of .249, which is only slightly less.

However, a 6mm ARC 108 gr match round has an SD of .261.

As expected, the sectional density ultimately comes down to bullet selection and velocity.

The higher velocity of the 6mm ARC means it will tend to have a higher SD. The SD is virtually the same when comparing similar rounds and isn't a significant concern for the average shooter.


While the 6.5 Grendel and 6mm ARC are similar, hunting is where you'll see one of the most remarkable differences between the two rounds.

The lighter bullets of the 6mm ARC make it an ideal cartridge for varmints and predators like coyotes because it's decently fast and flat, shooting at long distances. It's also capable of taking deer and other medium-game.

However, it's not recommended to hunt a larger animal than a deer at any considerable distance with the 6mm ARC because it doesn't have the necessary bullet weight to make an ethical kill.

Within 100 yards, it could take down an elk or wild hog at close range, but if it were me, I would prefer to hunt anything larger than a deer with the 6.5 Grendel.

The 6.5 Grendel has more options for heavier bullets which pack a better punch for big-game hunting but are overkill when hunting varmints.

When choosing between these calibers for hunting, it's determined by the size of the animal you plan to hunt.

The 6.5 Grendel is best for medium and large game animals like deer, elk, moose, bear, and caribou.

The 6mm ARC shines best when hunting varmints like prairie dogs, groundhogs, and coyotes.

Home Defense

For self-defense when venturing through bear country, the 6.5 Grendel should be your go-to instead of the 6mm ARC.

However, I don't recommend either round for home defense and self-defense in an urban area.

Both calibers are intended as rifle ammunition, and rifles are not the best Everyday Carry (EDC) weapon, especially concealed carry.

These calibers are also too likely to penetrate walls and strike innocent bystanders.

Instead, a pistol chambered in .45 ACP or 9mm is an excellent EDC weapon, and a 12 gauge or 20 gauge shotgun is much better for home defense situations.

For an SHTF scenario, either caliber would be ideal because they are designed for the versatile AR-15 platform.

This means you can easily carry lots of ammo in easy-to-access magazines and quickly and accurately send rounds down range when needed.

This category is also a tie.

Ammo and Rifle Cost and Availability

Cost and availability is the greatest difference between these calibers.

The 6mm ARC is still a new caliber, so finding a rifle and ammo chambered in it isn't easy because only a few manufacturers make either. This also drives the price of both ammo and rifle up.

A quality rifle chambered in 6mm ARC will cost you about $1,400.

The cheapest 6mm ARC ammo will cost about $1.30 per round.

The 6.5 Grendel has been around for nearly two decades and is still gaining popularity, so ammo and rifles are much more abundant than the 6mm ARC.

It still doesn't compare in popularity to the 223/5.56, though.

A quality AR-15 chambered in 6.5 Grendel will cost you $600+. Bolt action rifles are also chambered in 6.5 Grendel, so if you prefer a bolt gun over an AR-15, then the 6.5 Grendel should be your choice.

The cheap 6.5 Grendel ammo will still cost $1.00 per round.

Based solely on the availability and cost of the guns and ammo, the 6.5 Grendel separates itself from the 6mm ARC.

As more manufacturers begin to make the 6mm ARC, the availability should go up, and the price should go down, but for now, the 6.5 Grendel easily wins this category.


Reloading is an excellent way of controlling controllable variables. You can craft the ammo that your rifle cycles the best, unlike with factory loads.

It's also a way to save a little money on factory ammo if you're willing to put in the time it takes to handload correctly.

If you enjoy reloading, then either of these calibers will be an excellent choice. However, since the 6ARC is still a new round, it will be more challenging to find all the supplies you need to reload it.

Bullets for the 6.5 Grendel are becoming more common because the 6.5 Creedmoor is also gaining in popularity to reload, and they use the same bullets.

Finding reloading supplies such as brass, primers, bullets, and powder for the 6.5 Grendel will be easier than finding some of them for the 6 mm ARC.

A Brief 6mm ARC Development History

The 6mm Advanced Rifle Cartridge (ARC) is a newly developed round by Hornady. They wanted to create a round that could compete with the popular 223/5.56 in an AR-15, but it needed to shoot flatter at longer distances.

In 2020, Hornady released the 6mm ARC, and so far, it's lived up to the hype.

It's based on the .220 Russian, like the 6.5 Grendel, which is why they're such similar rounds.

A Brief 6.5 Grendel Development History

The 6.5 Grendel case has become a favorite of AR-15 shooters in the last couple of decades.

Released in 2003, it gained approval from Sporting Arms and Ammunition Manufacturer's Institute (SAAMI) in 2011.

In the last decade, it has gained a loyal following. So much so that some shooters don't believe the 6mm ARC can take enough of the market from the 6.5 Grendal to remain viable.

Who told those guys you couldn't enjoy both?

Are you curious how the 6.5 Grendel vs 308 debate turned out?

Final Shots: 6.5 Grendel vs 6mm ARC

When it comes to the 6mm ARC vs 6.5 Grendel, minute differences make each one stand out in certain circumstances.

The 6mm ARC is your best option if you're long-range target shooting and only occasionally go deer hunting because it shoots much flatter than the 6.5 Grendel.

However, if you're a big-game hunter, the 6.5 Grendel will perform better because it has a little more knockdown power due to the larger bullets.

In a perfect world, you could buy an upper for each caliber. If that's not feasible, the 6.5 Grendel is the better all-around caliber because of its versatility.
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Legend has it that a military unit approached Remington for help in developing a new cartridge that would allow heavier bullets to be fired from an M16-style weapon. The answer turned out to be the 6.8 Remington SPC.

This cartridge, which first appeared in civilian clothes in about 2004, allowed the M16 to be converted by simply replacing the top end. The acronym "SPC," incidentally, stands for "Special Purpose Carbine." It supplies more punch and reach than the ubiquitous 7.62x39 while still being mild enough to fulfill the assault rifle application--that is, to allow controlled full-automatic fire.


Several manufacturers are loading 6.8 Remington SPC ammo for civilian sale. The case is a shortened variation on the .30 Remington case that was introduced in 1906 and is now thoroughly obsolete in that form. The newly manufactured cases present an interesting problem. Cases manufactured by Remington use large rifle primers, while chose made by Hornady (and others) use small rifle primers.

It's not a serious problem if you are aware that the difference exists. Someone starting to load for this cartridge would be well advised to select cases that use either the small or the large primers, then stick to that type only In my tests I used both types of primers (in the appropriate cases, of course) and couldn't really see any difference in actual performance.


There are more than enough bullets available to cover your shooting and reloading needs. And don't let that metric designation fool you. The 6.8 is really the good old .270. That's good, because .270 bullets have been around for a long time. The useful ones are all at the light end of the .270s and range from 80 grains up to about 130 grains. Beyond 130 grains, the bullets are so long that if they are loaded to the maximum overall length allowed by the magazine length, the base of the bullet intrudes too deeply into the case and uses up too much of the available propellant volume. The result? Less than optimum performance.

Primer availability is no problem, but as we've mentioned above, you need to know which size your cases require. There is no shortage of suitable powder, but the small case limits the selection to the faster numbers in the rifle list. A gentleman who has been loading for the 6.8 for quite some time told me that he had decided that Hodgdon's 322 was the best overall choice. That powder worked well in my tests (see table), but there were a number of others that were equally useful.

The particular load referenced in the chart using IMR 3031 is there to illustrate what happens when too bulky a powder is used. The case is filled before you get up to the performance obtained with "better" powder choices.

It used to be that most all bullets had similar-weight jackets. That allowed brands to be interchanged without much of a problem. Modern high-performance bullets are made with jacket weights that are wildly different from one brand to the next While you can interchange any of the starting loads for the 130-grain bullets shown in the table, the maximum loads apply only to that specific bullet construction. Note that even different-style bullets from the same manufacturer show different results. As always, when changing anything, begin with the starting load and build up gradually and carefully in small increments while watching closely for any signs of trouble.6.8 REMINGTON SPC

Bullet/Weight (gr.) Primer Powder

Barnes Tripe-Shok (85) CCI-BR4 Accurate 1680

Speer TNT HP (90) Win. WSR Vihta Vuori N130

Hornady SP (100) Lapua SR Hodgdon H-4198

Nosler AccuBond (110) Fed. GM205M Hodgdon H-322

Barnes TSX Boatail (110) Win. WLR VihtaVuori N130

Hornady Varmint (110) Lapua SR Ramshot X-Terminator

Sierra HPBT Match (115) Fed. 205 Ramshot X-Terminator

Berger VLD Hunting (130) Rem. 7.5 Alliant R1-7

Barnes TSX Boattail (130) CCI-400 IMR 3031

Hornady InterLock (130) Rem. 9.5 Hodgdon Benchrest

Nosler AccuBond (130) Fed. 205 Hodgdon H-322

Nosler Ballistic Tip (130) Rem. 9.5 Accurate 2230

Nosler E-Tip (130) Win. WLR Norma 201

Sierra Spitzer (130) CCI-400 Winchester 748

Speer Grand Slam (130) Fed. 205 RamShot TAC

Speer Hot-Cor (130) CCI-200 Allliant R1-7

Bullet/Weight (gr.) Case Starting Load (gr.)

Barnes Tripe-Shok (85) Silver State Armory 24.0

Speer TNT HP (90) Frontier 24.0

Hornady SP (100) Frontier 22.0

Nosler AccuBond (110) Silver State Armory 23.0

Barnes TSX Boatail (110) Remington 22.5

Hornady Varmint (110) Silver State Armory 25.0

Sierra HPBT Match (115) Frontier 25.0

Berger VLD Hunting (130) Frontier 21.0

Barnes TSX Boattail (130) Frontier 23.0

Hornady InterLock (130) Remington 25.0

Nosler AccuBond (130) Silver State Armory 22.0

Nosler Ballistic Tip (130) Remington 23.0

Nosler E-Tip (130) Remington 23.0

Sierra Spitzer (130) Frontier 25.0

Speer Grand Slam (130) Silver State Armory 25.0

Speer Hot-Cor (130) Remington 21.0

Bullet/Weight (gr.) Maximum Load (gr.)

Barnes Tripe-Shok (85) 28.0

Speer TNT HP (90) 28.0

Hornady SP (100) 26.0

Nosler AccuBond (110) 27.5

Barnes TSX Boatail (110) 25.0

Hornady Varmint (110) 29.5

Sierra HPBT Match (115) 29.0

Berger VLD Hunting (130) 24.5

Barnes TSX Boattail (130) 25.5*

Hornady InterLock (130) 28.0

Nosler AccuBond (130) 26.0

Nosler Ballistic Tip (130) 27.5

Nosler E-Tip (130) 27.0

Sierra Spitzer (130) 29.0

Speer Grand Slam (130) 29.0

Speer Hot-Cor (130) 24.0

Bullet/Weight (gr.) Max. Load Velocity (fps)

Barnes Tripe-Shok (85) 3,100

Speer TNT HP (90) 2,950

Hornady SP (100) 2,850

Nosler AccuBond (110) 2,725

Barnes TSX Boatail (110) 2,675

Hornady Varmint (110) 2,725

Sierra HPBT Match (115) 2,650

Berger VLD Hunting (130) 2,500

Barnes TSX Boattail (130) 2,275

Hornady InterLock (130) 2,550

Nosler AccuBond (130) 2,450

Nosler Ballistic Tip (130) 2,500

Nosler E-Tip (130) 2,400

Sierra Spitzer (130) 2,550

Speer Grand Slam (130) 2,550

Speer Hot-Cor (130) 2,450

All data derived from a 24-inch pressure barrel.* Powder volume limited

When developing loads for any semiautomatic weapon, I like to verify that the starting loads will function the weapon. I had to bump up a couple of my original starring loads (developed in a pressure barrel) by a grain to make the Ruger Ranch Rifle--that I was using for function rests--cycle cleanly. The starting loads shown in the table have all been function tested and at least operate that particular rifle. Since guns of even the same model differ in how easily they cycle, you might find some of these starting loads too mild. Well, it's a lot better to start too mild than too strong.

During the function tests I also did a brief accuracy test on the Ruger. While it didn't group quite as tight as the pressure barrel (no big surprise), the group was just about an inch at 100 yards.

The 6.8 Remington SPC cartridge has been around for long enough that dies are not a problem. This month's examples came from Lyman. I did find that I had to carefully control the headspace by adjusting the sizing die out a bit because it was easy to get too much headspace, resulting in weak primer strikes. Once I got the correct length for that gun sorted our, everything was fine.


The loads in the table were developed in a 24-inch pressure barrel. The velocities obtained in the Ranch Rifle's 16 1/2-inch barrel averaged just about 100 fps slower. That's not as much loss as you might expect for that barrel-length difference, but the small case is the reason for that. A larger-volume ease would have showed a bigger loss.

Energy-wise, the 6.8 SPC is pretty much identical to the time-honored .30-30 Winchester, so it goes without saying that it's an adequate deer (or hog) cartridge. While I know some adventurous types are going to try it on larger game, I would rather see folks using a little too much gun rather than too little. And I certainly cannot recommend that any try the 6.8 Remington SPC on elk or bear.

This is a nice little cartridge, with decent performance for its size. There are plenty of components, no serious problems with reloading and enough performance to handle heavy varmint (read:predator) or deer hunting applications.

WARNING: The loads shown here are safe only in the guns for which they were developed. Neither the author nor InterMedia Outdoors Inc. assumes any liability for accidents or injury resulting from the use or misuse of this data.

COPYRIGHT 2009 InterMedia Outdoors, Inc.
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6.8 SPC vs 6.5 Grendel: Enhancing The AR-15 Platform

In the early 2000’s, there was a big push from the U.S. Army to adapt new, more powerful cartridges to the M4 carbine. This initiative was preempted by battlefield reports of enemy combatants taking multiple hits from 5.56 NATO rounds and remaining combat effective.

The 6.8 Remington Special Purpose Cartridge (SPC) and 6.5 Grendel were two new cartridges developed to increase the lethality of the AR-15 platform. Although their terminal ballistics were impressive, neither cartridge was adopted for mainstream military use.

The 6.8SPC and 6.5 Grendel may not have seen frontline combat, but they have enjoyed moderate commercial success from shooters who want a little more “oomph” out of their semi-automatic sporting rifles.

However, many 2A enthusiasts are perplexed over which cartridge to select for their new AR-15 if they want something other than the standard 5.56 NATO/223 Remington chambering. Is the 6.8 SPC better than 6.5 Grendel? Or does the 6.5 come out on top?

In this article, we will discuss the merits and shortcomings of the 6.8 SPC and 6.5 Grendel and how they can meet your shooting needs.

What is the difference between 6.8 SPC and 6.5 Grendel?

The main differences between the 6.8 SPC and 6.5 Grendel are the bullet diameters each cartridge fires and their intended purpose. The 6.8 SPC fires 0.277” diameter bullets compared to 0.264” for 6.5 Grendel. Furthermore, the 6.8 SPC was optimized for close quarters battle (CQB) conditions and to be employed in short barreled rifles (16” or less) whereas the 6.5 Grendel is at its best when fired from a 20 inch barrel at longer ranges.

Cartridge Specs

When evaluating centerfire rifle cartridges, it’s a good idea to analyze the cartridge specs to gain more knowledge of each.

The biggest difference between the 6.5 Grendel vs 6.8 SPC are the bullets they fire.

The 6.5 Grendel fires the sleek, aerodynamic 0.264” diameter bullets also fired by cartridges like the 6.5 Creedmoor, 260 Remington, and 6.5 PRC just to name a few. Grendel ammo is typically loaded with bullet weights ranging between 90-130 gr with the 100, 110, 120, and 123 gr offerings being the most popular.

On the other hand, the 6.8 SPC fired a wider 0.277” diameter bullet also utilized by cartridges like the 270 Winchester, 6.8 Western, and the new SIG 277 Fury. The 6.8 SPC typically fires bullet weights between 75-120 gr with the 85, 100, 110, 115, and 120 gr factory loads being the most common.

Both the 6.5 Grendel and 6.8 SPC have different base diameters of 0.439” and 0.422”, respectively. This means that both cartridges require a bolt change when performing a conversion on an AR-15.

The 6.8SPC case is slightly longer, measuring 1.687”, than the 6.5 Grendel cartridge case, measuring 1.52”. Both cartridges have the same overall length of 2.26” as this is the maximum allowable cartridge length for the AR-15 platform. The longer case length for the SPC round means that more of the bullet must be seated inside the case to meet the overall length requirement. This, in turn, robs the cartridge of some case capacity and ballistic performance. On the other hand, the design of the 6.5 Grendel case allows for longer, high ballistic coefficient bullets to be utilized without having to seat them deep inside the case. This is a similar tactic that the ballisticians at Hornady used when developing the 300 PRC.

Even though the 6.8 SPC has a longer case, it has virtually the same case capacity as the 6.5 Grendel at 35 gr. However, the 6.8 SPC is rated to handle slightly higher chamber pressures of 55,000 psi vs 52,000 psi for the Grendel per SAAMI specs.


The 6.8 SPC will generally have slightly less recoil than the 6.5 Grendel.

Recoil is an important consideration when purchasing a new rifle as a round with heavy recoil will be more difficult to control and will slow your rate of follow up shots.

Recoil is affected primarily by muzzle velocity (FPS), powder charge, bullet weight, and rifle weight.

The 6.5 Grendel will typically have slightly more free recoil energy than the 6.8 SPC as the Grendel can handle slightly more powder (since the bullets aren’t seated as deep) and are fired at higher muzzle velocities.

For example, a 6.5 Grendel 123 gr Hornady SST fired from a 6-pound AR-15 at 2,500 fps will have a free recoil energy of around 11 ft-lbs compared to 9 ft-lbs for a 6.8 SPC 120 gr SST fired at 2,400 fps from the same rifle.

It should be noted that both cartridges are considered low recoil and shooters can enjoy a full day at the range shooting both without any adverse shoulder-bruising effects. However, for recoil sensitive shooters, the 6.8 SPC is typically the better option.

Muzzle Velocity and Kinetic Energy

Generally, the 6.5 Grendel will have higher muzzle energy and muzzle velocity than the 6.8 SPC.

As the 6.5 Grendel was designed for long range target shooting, it requires better ballistics to reach its intended target. However, manufacturer’s ballistic data can sometimes be misleading due to differences in barrel length.

Take for example the 123 gr SST Hornady factory load for 6.5 Grendel and 120 SST for 6.8 SPC. Hornady states that the 123 gr 6.5 Grendel round will have a muzzle velocity of 2,580 fps and muzzle energy of 1,818 ft-lbs when fired from a 24” barrel. On the other hand, the 6.8 SPC 120 gr SST is reported as having a muzzle velocity of 2,460 fps and energy of 1,612 ft-lbs from a 16” barrel.

The difference in barrel length is quite significant and showcases one of the major differences between these two cartridges. The 6.8 SPC was specifically designed for use in the M4 carbine, which has a 14.5” barrel length, while Alexander Arms (the developer of the 6.5 Grendel) recommends using a barrel of no less than 20” for its cartridge.

Those familiar with long-range shooting know that a long barrel is preferred to a short one as bullets fired from a shorter barrel typically have a lower muzzle velocity. Although the 6.8 SPC can reach its peak performance in a short barrel, the 6.5 Grendel needs the extra barrel length to reach its full potential.

If you were to fire a 6.5 Grendel form a 16 inch barrel, most of its ballistic advantage over the 6.8 SPC is erased and both cartridges would have similar muzzle velocities and muzzle energies.


When fired from a longer barrel, the 6.5 Grendel has a flatter trajectory at all ranges compared to the 6.8 SPC.

Trajectory is how we quantify a bullet’s flight path as it travels downrange measured in inches of bullet drop.

Obviously, a flatter shooting cartridge is preferred for long-range shooting, as a shooter will require fewer adjustments to their optics to compensate for bullet drop. Having a flatter trajectory also means that a cartridge will be more forgiving of ranging mistakes.

At shorter ranges under 200 yards, both cartridges have virtually identical trajectories. However, with its higher muzzle velocity and higher ballistic coefficient bullets, the 6.5 Grendel simply dominates the 6.8 SPC at longer ranges. Assuming a 100 yard zero for both cartridges, at 500 yards the 6.5 Grendel has experienced -64” of bullet drop compared to -79” for the 6.8 SPC.

Ballistic Coefficient

The 6.5 Grendel generally will have a higher ballistic coefficient as it was designed to fire longer, more aerodynamic bullets.

Ballistic coefficient (BC) is a measure of how well a bullet resists wind drift and air resistance. Put another way, it’s a numeric representation of how aerodynamic a bullet is. A high BC is preferred as this means the bullet will buck the wind easier.

Generally, heavy bullets will have a higher BC as it takes more force to disrupt the flight of a heavier bullet than a lighter one. Ballistic coefficient varies from bullet to bullet based on design, weight, and other factors that are beyond the scope of this article.

The ability of 6.5mm bullets to resist wind drift is well documented with the rise in popularity of the 6.5 Creedmoor. As the 6.5 Grendel can fire the same sleek bullets as the Creedmoor, it is not surprising that the 6.5 Grendel will outperform the 6.8 SPC in terms of BC.

Take for example the Barnes Tipped TSX bullets, which are extremely popular with big game hunters. The 120 gr 6.5 Grendel TSX bullet has a BC of 0.412 compared to 0.377 for the 110 gr 6.8 SPC TSX bullet.

Sectional Density

The 6.5 Grendel will typically have a higher sectional density and penetrate deeper than the 6.8 SPC.

Sectional Density (SD) is the measure of how well a bullet penetrates a target. This is extremely important when hunting big and medium sized game, as you need a bullet that can punch through thick hide, bone, and sinew.

Sectional density is calculated by comparing the bullet weight and the bullet diameter. The higher the SD the deeper the bullet will penetrate into the target. This is a simplified view of penetration as there are other factors to consider, such as bullet expansion and high velocity.

As the 6.5 utilizes a longer bullet design, it is able to focus its higher muzzle energy onto a smaller area and thereby increasing its penetration.

For example, the 100 gr Nosler Ballistic Tip bullet for 6.5 Grendel has a SD of 0.205 while a 100 gr Nosler AccuBond for 6.8 SPC has a SD of 0.186.

Although the 6.5 Grendel does generally have a higher sectional density than the 6.8 SPC, the difference is so minor that it is unlikely any hunter, whitetail, or feral hogs will be able to tell the difference.


Although the 6.5 Grendel and 6.8 SPC have not been issued to GI’s on the front lines, hunters have discovered the power and flexibility each have as a hunting cartridge.

Internet forums are always ablaze in debates over which is better for whitetail, hogs, and varmints. When it comes to 6.5 Grendel and 6.8 SPC, both cartridges are exceptional at deer hunting while the 6.5 Grendel is more suited for varmints and the 6.8 SPC has made a name for itself in hog hunting circles.

With its long range capabilities and flat trajectory, the 6.5 Grendel is an excellent choice for varmint hunting. With its longer effective range of over 1,000 yards and better ballistic performance, the 6.5 really excels at dispatching thin skinned varmints and longer ranges. This is not to say that the 6.8 cannot be used on varmints, but the superior ballistic coefficient of Grendel ammo really makes it an attractive choice for long-range shooting.

For whitetail and mule deer, both the 6.5 and the 6.8 are exceptional choices at typical hunting ranges. The 6.8 SPC has an effective range of around 200 yards for deer hunting while the 6.5 Grendel can harvest deer out to 400 yards. However, the 6.8 SPC gets the nod here as its terminal performance on game animals is slightly better than the 6.5 and the 6.8 can achieve these results when fired from a shorter barrel. When sitting in a tree stand or maneuvering through thick brush on a stalk, a lighter and more compact rifle is easier to handle. As the 6.8 SPC is optimized for hunting with a 16 inch barrel, it is the better choice when hunting in heavily wooded areas like those encountered in the Midwest or Pacific Northwest. However, if longer shots need to be taken like those on the Great Plains and barrel length is less of an issue, then the 6.5 Grendel would be a better choice.

For hog hunting in the southern states, the 6.8 SPC has quite the reputation as a potent porcine slaying round. As improved terminal performance is preferred on larger animals, the 6.8 finds itself in a great position when facing down a herd of unruly hogs intent on destroying a farmer’s field in a night. With its lower recoil impulse, the 6.8 SPC allows for faster follow-up shots or multiple target engagements more effectively than the 6.5 Grendel. Furthermore, the 6.5’s longer effective range is less important when hog hunting, as most shots are within 250 yards or less. For hogs, it’s clear that the 6.8 SPC is the better choice.

Ammo and Rifle Cost/Availability

As far as ammo availability is concerned, both the 6.8 SPC and 6.5 Grendel are about the same. Most of your major ammo manufacturers like Remington, S&B, Federal, Nosler, and Barnes have factory ammo for both cartridges.

In terms of cost, inexpensive FMJ ammo will be slightly less expensive for the 6.8 SPC at around $1.40/round compared to $1.70/round for 6.5 Grendel. For premium hunting ammo, both cartridges are essentially equivalent starting close to $2/round and going up from there.

In terms of rifles, the 6.5 Grendel has a slight edge over the 6.8 SPC in terms of varieties and numbers.

Premium AR-15 manufacturers like Wilson Combat, LWRC, Savage, and Barrett have offerings in both 6.5 and 6.8, with dedicated rifles and upper receivers.

If you want a bolt gun, the 6.5 Grendel is your only option as the 6.8 SPC is limited to the AR-15 only at the time of writing. The Ruger American Ranch and Predator, Howa Mini, and CZ 527 are currently the only bolt action rifles available in 6.5 Grendel.


Reloading is one way that shooters can decrease their overall cost per round for both cartridges.

Brass, reloading dies, primers, and powders are readily available for each. However, when it comes to bullet selection the 6.5 has a slight edge due to the proliferation and popularity of the 6.5 Creedmoor. As the Grendel and Creedmoor fire the same bullet diameter, 6.5 Grendel shooters will enjoy a wider array of bullet options and weights than 6.8 shooters.

However, as the U.S. Army recently adopted the 277 SIG Fury as their new battle cartridge, the future looks bright for fans of the 6.8 caliber bullet.

Handloaders also have the opportunity to explore the full capability of the 6.8 SPC, as most factory ammo is not loaded to full power due to chamber design flaws experienced with the failed rollout of the first iteration of the 6.8.

A Brief History of 6.5 Grendel

Ever since the adoption of the 223 Remington/5.56 NATO cartridge by the US armed forces, critics have questioned the combat effectiveness and terminal ballistics of the 22-caliber round. As a result, several intermediate cartridges have been adapted to the AR-15 platform such as the 300 Blackout and 6.8 SPC in an attempt to bridge the gap between the 223 Reminton and 308 Winchester.

Never one to back down from a challenge, British/American armorer Bill Alexander of Alexander Arms debuted the 6.5 Grendel in May 2003 at the Blackwater training facility in North Carolina. Alexander Arms also utilized the services of competitive shooter Arne Brennan and senior ballistician Janne Pohjoispää of Lapua in development of the new rifle cartridge.

Bill Alexander was clearly a fan of mythology, as Grendel is the name of a monster in the British epic poem, Beowulf. Staying true to form, Alexander Arms also developed the 50 Beowulf cartridge for the AR-15 as well.

The goal of the 6.5 Grendel was to develop an intermediate cartridge that extended the effective range of AR-15 rifles out past 800 yards. Utilizing the same higher ballistic coefficient 0.264” diameter bullets used by the 6.5 Creedmoor, the 6.5 Grendel is capable or maintaining MOA-level accuracy and supersonic velocities out to 1,200 yards with half the recoil of the 308 Win.

Descended from the 6.5mm PPC, which itself was developed from the 220 Russian and 7.62x39mm, the 6.5 Grendel has a wider case head than the 223 Remington and requires a non-standard AR-15 bolt and specialized magazines for use in AR-15 rifles.

Wide-spread adoption of the 6.5 Grendel was somewhat hindered by Bill Alexander himself, as he insisted that the cartridge be trademarked, and therefore could not be standardized by SAAMI. However, Alexander Arms in collaboration with Hornady Ammunition, registered the 6.5 Grendel with SAAMI in 2010. This allowed other manufacturers to create and sell 6.5 Grendel ammo, greatly expanding the reach of the cartridge.

As the 6.5 Grendel is still a relatively new cartridge on the market, it has developed a stalwart following in the shooting community who enjoy the terminal ballistics of a 308 Win without having to upgrade to an AR-10.

Although the 6.5 Grendel has not yet been adopted by the US military, the Serbian military is currently conducting tests in accordance with adopting the 6.5 Grendel in their new M17 Zastava battle rifles.

With exceptional long range capability, barrel life, and MOA-level accuracy, the 6.5 Grendel is an excellent choice if you’re looking to upgrade your AR-15 platform to something that has a bit more stopping power than a 223 Rem.

To read more about the 6.5 Grendel, check out the full history on our 6.5 Grendel history page.

If you’d like to learn more about how the 6.5 Grendel compares to other calibers, check out these articles below:
  • 6.5 Grendel vs 308
  • 6.5 Grendel vs 223 vs 5.56
A Brief History of 6.8 SPC

The 6.8 Remington Special Purpose Cartridge (6.8 SPC, 6.8 SPC II, or 6.8x43mm) was developed in 2004 as a joint operation between Remington Arms, US Special Operations Command (USCOCOM), and the U.S. Army Marksmanship unit.

The goal of the cartridge was to increase the terminal performance of the M4 carbine, as urban close quarters battle (CQB) in the 2nd Iraq War had showcased some deficiencies in the 5.56x45mm NATO/223 Remington cartridge.

Initial designs for the 6.8 SPC came from Master Sgt. Steve Holland and Chris Murray, who used the 30 Remington as a parent case that was modified to fit in standard M4 magazines.

One key design point was that the 6.8 SPC was developed to perform better in short-barreled rifles (SBR) like the M4 carbine, as opposed to the longer M16 assault rifle.

Fired from an M4, the 6.8 SPC can deliver almost 45% more kinetic energy into its target than standard 62 gr M855 NATO ammunition.

Although the 6.8 SPC seemed to be a potent answer to the 5.56 NATO terminal performance issue, there were some problems with its implementation.

Sadly, the chamber designs on the original 6.8 SPC cartridge were somewhat inaccurate, and the biggest issue was the free bore space at the mouth of the chamber.

The original chamber designs called for 0.050” of free bore, but combined with a 1:10 twist rate barrel, pressure issues began to creep up. Initial reports claimed that the rounds were only around 200 psi above the maximum 55,000 psi pressure limits, but if the military learned anything from Vietnam, it was to follow specs to the letter.

Remington sought to remedy the issue the best way they saw fit, which was to underload the ammo. As no one wants to shoot rounds that don’t live up to their full potential, the order was given for “Taps” to be played and the 6.8 SPC project was not adopted by the U.S. military.

However, in all the excitement over the new 6.8 SPC, several civilian firearm manufactures clambered to release rifles chambered in the new hotshot round before SAAMI had officially adopted the cartridge. With numerous faulty rifles in the wild, the only action SAAMI could take was to sanction the round.

This is not to say that original 6.8 SPC rifles won’t function properly, but there is the potential for a critical pressure failure when using full power rounds.

The answer was the 6.8 SPC II.

The 6.8 SPC II added an additional 0.050” of free bore to the chamber and decreased the barrel twist rate to 1:11. This completely solved the pressure issues experienced with the original design. All current rifles chambered in 6.8 SPC are actually chambered in 6.8 SPC II.

The 6.8 SPC II offers hunters an excellent intermediate cartridge option for small to medium game, while handloaders love the cartridge for its versatility. Capable of firing 85-140 grain bullets, the 6.8 SPC II allows reloaders the ability to load their ammo light for plinking and hot for hunting.

Although most factory loads will be loaded light (due to original 6.8 SPC rifles still in the wild), the 6.8 SPC II sits in the sweet spot between the ubiquitous 0.308” and diminutive 0.224” calibers. This offers shooters the power they need for medium game hunting without the increased recoil and heavier firearm (AR-10) associated with the 0.308.

To read more about the 6.8 Remington SPC, check out the full history of the cartridge on our 6.8 SPC history page.
Drag Function: G1
Ballistic Coefficient: 0.400
Bullet Weight: 120 gr
Initial Velocity: 2500 fps
Sight Height : 1.5 in
Shooting Angle: 0°
Wind Speed: 10 mph
Wind Angle: 90°
Zero Range: 200 yd
Chart Range: 500 yd
Maximum Range: 5113 yd
Step Size: 25 yd
International Standard Atmosphere
Altitude: Sea Level (0 ft)
Barometric Pressure: 29.92 Hg
Temperature: 59° F
Relative Humidity: 50%
Speed of Sound: 1116 fps


Final Shots: 6.5 Grendel vs 6.8 SPC

The 6.5 Grendel and 6.8 SPC are two intermediate cartridges developed to increase the lethality of the AR-15 platform. Both cartridges achieved this goal and have better ballistics than the anemic 5.56 NATO.

Adapting new cartridges to the AR-15 is nothing new, as other offerings like the 224 Valkyrie and 300 Blackout also look to enhance the breadth and depth of ammo options for the most popular sporting rifle in the world.

The 6.5 Grendel is a great option for long range target shooting and an extremely capable hunting cartridge. Its sleek 6.5mm bullets have incredibly high ballistic coefficients and sectional densities that make the Grendel round a potent long-range shooting threat. The one limiting factor to the 6.5 Grendel is its reliance on a longer barrel length of 20 inches or more to achieve its full potential.

The 6.8 Remington Special Purpose Cartridge focuses more on terminal performance in a short barreled rifle (SBR) over long range performance. Optimized for the M4 carbine with a 16 inch barrel or less, the 6.8 SPC offers shooters a powerful cartridge that has 40% more kinetic energy than the 5.56 NATO within 300 yards in a tight, lightweight package. However, the 6.8 is less effective at longer ranges as it hemorrhages energy and velocity as distances over 500 yards.

Selecting the right cartridge for your needs primarily centers on what ranges you expect to shoot at. For typical hunting ranges of 300 yards or less, the 6.8 SPC has a lot to offer with lower recoil and better terminal ballistics in a shorter rifle. However, if you expect to shoot over 300 yards and don’t mind using a longer barrel length, then the 6.5 Grendel offers you a cartridge that can extend your effective range out past 500 yards.

Regardless of which cartridge you choose, make sure you stock up on ammunition here at Ammo.com and I’ll see you on the range!

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if your goal is to have an AR 15 chambered in a cartridge that will be a big boost up in performance over your typical 223 rem
there's several good options, like the 300 blackout, the 350 legend, 400 legend and the 6.8 spc all come to mind'
yes there are other options like the AR15 can be chambered in 6.5 grendel, 7.62/39,

all would work with proper handloaded ammo but the first three I listed would provide a bit better punch at short or moderate ranges,
the 6.8 spc would potentially have extended the effective range and had lower recoil.

in all cartridges barrels of 20"-24" provide noticeably better results than shorter 16" barrels

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I believe in looking at both sides of any discussion,
no AR15 compatible cartridge matches the longer range punch of a 308 win, or 6.5 Creedmoor in an M1A1
the 6.8 spc was developed to provide military special ops, to provide combat troops with a more lethal carbine,
with a flatter trajectory and more lethal cartridge, in the AR CARBINE platform.
than a 223 rem or 7.62/39 like the Russians/terrorists use, that fit the AR15,platform
keep in mind realistically most people can't consistently hit any target much past 300 yards
for use in the typical 0-400 yard combat ranges the 6.8spc, with very minimal changes BEING REQUIRED to the AR15 rifles.
barrels ,bolt heads and magazines were all that is needed changing to the 6.8 SPC
keep in mind careful projectile selection makes a huge difference in results\
you'll generally need to select a 6.8mm bullet that's 5-10 grains heavier to match too a 6.5mm bullet to get a similar ballistic
what you might think is a minor difference in bullets compared, can make a noticeable difference.
BUT it can, compare very similar ballistic coefficient bullets not similar weights

you can't just compare the same weight bullets, you need to select bullets with very similar ballistic coefficients.pushed to similar muzzle velocities
with similar ballistic characteristics(coefficients)heavier projectiles with higher ballistic coefficients allow those projectiles to maintain velocity and impact energy out to longer distance's:like:yes, much higher velocity through use of lighter weight projectiles at shorter distances with those lighter weight projectiles generally look more impressive, but you usually won't know the target/ or your opponents s range before its engaged
And after a few times on the rifle range I have to state I have a decided preference for the 6.8 spc
as it seems to feed flawlessly, and allow a higher magazine capacity in the standard AR15 SIZE 30 round mag size,
clone modified for the different case dimensions,
mags adapted to the different case size, will have a different capacity and,
if it either cartridge option is used, a bit heavier projectile in either cartridge option tends to extend the effective range vs if a lighter projectile at much higher velocity is used. lighter weight projectiles at marginally higher velocity provide higher initial impact energy ,at least for the first few hundred yards , but after that shorter range (generally 0-400 yards or so) loose penetration rather rapidly, compared to the heavier projectile options.
G1 Ballistic Coefficient0.463 129 grain 6.8mm

G1 Ballistic Coefficient0.468 127 grain 6.5mm
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