how do you know when you have enough roll crimp?

[grumpyvette]

"GRUMPY? , how do you know when you have enough roll crimp? "

basically a crimp on the case is designed to prevent the bullets movement from any recoil generated by the recoil a gun generates as its fired, as its sitting in a magazine or a revolvers cylinder, or during chambering of the cartridge,in auto pistol.
your bullets need to have nearly identical resistance to movement until the pressure of the ignited powder forces them out of the case. none of your bullets should move until the cartridge actually is fired,so your over all cartridge length doesn,t change, which is what your trying to do, the problem is that under hard recoil an unfired cartridge almost acts like its in a kinetic bullet puller if the crimps not got a really good grip and the bullet moves a bit forward in its case, this can and does lock up a revolvers cylinder and the lack of resistance can and does prevent consistent powder ignition.
youll get the idea real fast if you screw it up, theres two common types of crimp a roll crimp which is usually used in revolvers that head space on a cartridge rim, and a taper crimp usually used with automatics that head space on the case mouth
You must crimp all cartridges intended to be used in a revolver. The main reason is: upon recoil the unfired bullets want to back out of their cases. They have this tendency because they are obeying one of Newton's laws... "a body at rest wants to remain at rest" etc. When a bullet backs out sufficiently from its case, it renders the revolver USELESS! The cylinder will not rotate because of the bullet(s) protruding from out in front...hitting the sides of the frame as the cylinder rotates
The reason you want to crimp is to increase neck tension. Neck tension will add resistance as the bullet starts its movement out of the case allowing pressure to build and ensuring complete combustion of the powder.

A roll crimp is the most common type of crimp for a revolver cartridge. A semi-auto round normally uses a taper crimp to keep the bullet form being pushed back into the casing. This is the exact opposite of a revolver where an un-crimped bullet may be pulled out of the casing. A crimp will also ensure reliable feeding in a semi-auto.
reads these

http://membres.multimania.fr/shooter/re ... chargt.htm

http://www.exteriorballistics.com/reloa ... /crimp.cfm

http://projects.nfstc.org/firearms/modu ... t09_04.htm

http://www.thefirearmsforum.com/showthread.php?t=76154

http://www.dave-cushman.net/shot/bullet ... mping.html

 

[rlphvac]

I had this happen with factory CCI loads on my Ruger LCR 357 I called them about it and they said this happens with small revolvers now I have fired thousands of other rounds from this gun & the CCI is the only one that did this

 

[Grumpy]

smaller and lighter weight hand guns offer less mass and tend to recoil faster or accelerate, under the forces generated by the discharge of a cartridge faster this allows the bullets in remaining cartridges, that have mass to resist the acceleration, the result is that a loose crimp allows repeated firings to allow the case to back off the bullets still in the gun, a firm crimp prevents the bullet moving from the case untill the cartridge is actually fired!
because both the depth of the case insertion and the bullet seated depth are easily adjustable on your reloading machine the exact crimp and over all cartridge length are adjustable, allowing a firm crimp to be applied,to answer the question directly you want the minimum crimp that assures a 100% reliable bullet retention in its original loaded location, in the case

THESE two presses work great the upper ones current production

http://www.natchezss.com/rcbs-rock-chucker-supreme-press.html
this press is only available used , but its in my opinion, it is a slightly better design, worth buying if found at a decent price

heres a recoil calculator.

http://handloads.com/calc/recoil.asp
if we take the ammo I generally hunt with in my 44 mag revolver its pushing a 300 grain cast bullet at a bit over 1400 fps, if that revolver weights 3 lbs or ( 48 OZ)

if we take the ammo I generally hunt with in my 44 mag revolver its pushing a 300 grain cast bullet at a bit over 1400 fps, if that revolver weights roughly
36 OZ
theres about a 36% increase in the hand gun felt recoil as the revolver jumps as the bullet leave the gun due to the lower mass vs energy as the bullet leaves the gun, this extra speed will tend to pull loose crimp bullets from cases

when you hand load you can adjust the crimp depth and how and were on the bullet surface its applied and cartridge over all length, all of which effect the pull resistance.
a loose crimp also tends to cause inconsistent ignition and thus inconsistent velocities if slow burning powders are used that generally maximize velocity.
during the reload process the last die is used to seat the bullet into the case, at the point the case is moving up into the die and the bullet is a couple thousands of an inch from reaching its full upward travel the case mouth encounters a restrictive tapered inner ring in the the die throat that forces the mouth of the cartridge inward at an angle (tapper crimp)or along a curved radius(roll crimp) this inward crimp or reduction of the inner case moth diameter is generally slightly adjustable by simply changing the depth the case moves upward into the seating die, as the bullet is seated as theres a threaded spindle that allows you to adjust bullet seat depth, in relation to crimp.

http://projects.nfstc.org/firearms/module05/fir_m05_t09_04.htm

yeah as usual theres links with info
http://www.massreloading.com/Handgun_Cartridge_Crimping.html

http://www.realguns.com/Commentary/comar64.htm

http://reloadingtips.com/how_to/crimping_revolvers.htm

http://www.chuckhawks.com/adjust_reloading_dies.htm

http://leeprecision.com/reloading-dies/hand-gun-dies/lee-carbide-factory-crimp-die/