The 6.8 SPC is also loaded to a slightly higher pressure than the 6.5 Grendel (55,000psi vs 52,000psi).
the ideal 6.8 spc will have a 20"-24" barrel to take full advantage of the cartridges higher pressure and bullet designs
6.5 Grendel vs 6.8 SPC Ballistics
Those differences in the external dimensions of the 6.5 Grendel and 6.8 SPC translate into some interesting differences in their ballistic performance.
This is illustrated in the table below comparing Hornady factory ammunition. The 6.5 Grendel load uses a 123gr ELD-M (.506 BC) while the 6.8 SPC load uses a 120gr SST (.400 BC).
Note that Hornady advertises a velocity of 2,580fps for this particular 6.5 Grendel load, but uses a 24″ barrel to do so. At the same time, they advertise a velocity of 2,460fps for their 6.8 SPC load with a 16″ barrel. In the interest of conducting as close to an “apples to apples” comparison as possible, I also included ballistic data for that same Hornady 6.5 Grendel load with a velocity of 2,369fps
from a 16″ barrel.
All three loads used a 100 yard zero.
As you can see, the 6.5 Grendel load using a 24″ barrel starts off with about a 12% edge in kinetic energy that increases with range (about 40% more at 500 yards). This is due to the fact that this particular load uses a heavier bullet with a higher ballistic coefficient and a faster muzzle velocity.
Additionally, that particular 6.5 Grendel load has a flatter trajectory at all ranges. Like with kinetic energy, this advantage grows as range increases: it has about 1″ less bullet drop at 200 yards, about 3″ less at 300 yards, about 7.5″ less at 400 yards, and almost 15″ less bullet drop at 500 yards.
However, things change quite a bit when the 6.5 Grendel is used in a shorter barreled rifle.
In that case, the 6.8 SPC actually starts off with about 5% more kinetic energy. The 6.5 Grendel is still using a heavier and more aerodynamic bullet though, so that slight advantage in kinetic energy decreases and eventually flips in favor of the 6.5 Grendel between 100 and 200 yards. At 500 yards, the 6.5 Grendel has about 15% more kinetic energy.
When fired from a 16″ barrel, the 6.5 Grendel also has almost exactly the same trajectory as the 6.8 SPC.
All that being said, the gap in performance between the cartridges is pretty minimal at ranges inside 200 yards.
The chart below compares how much a 10 mile per hour crosswind impacts those same 6.5 Grendel and 6.8 SPC loads out to 500 yards.
Once again we see that the 6.5 Grendel outperforms the 6.8 SPC in terms of wind drift at longer range. This holds true for both barrel lengths, though the gap in performance is smaller when the 6.5 Grendel is fired from a shorter barrel.
However, the 6.8 SPC is still a very effective cartridge at short to moderate range.
The table below compares the recoil produced by very similar loads to the ones compared above for each cartridge when fired from identical rifles.
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