To crimp or not to crimp....


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Vic
November 16, 2006, 02:19 AM
I know this subject has been beat to death here but I gotta ask. The calibers in question are as follows:

5.56mm
7.62 (.308Win)
30-06

Applications are AR15's and M1 Garand's. I know the military crimps but is it really that important since the 7.62 and the 5.56 are not run in FA weapons. Normally in the 5.56/7.62, I do not crimp HP's or soft point but I do crimp FMJ 55/62...147/150 gr bullets. I would like some opinions on pressure differences and other vairiables concerning this topic. TIA!:what:

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db_tanker
November 16, 2006, 06:37 AM
In semi-autos its a good idea to crimp the bullets due to recoil possibly "adjusting" the bullet seating depth...

Deeper the bullet, possible compression, possible pressure spike, and finally possible rapid dissasembly of rifle being used.

Bolt rifles are a diffrent story...I don't due to my loading them one at a time...


NOW...there are some loads that you might actually need to crimp...this is due to the powder type being used...one powder that comes to mind is H-110/296...it needs a good crimp to get proper ignition. I have worked up loads in a 44 mag and 357 mag in single shot pistols and there is a pretty noticable diffrence in the crimped and uncrimped loads. first there is more residue in the uncrimped loads, the groups were larger and finally the deviation was much greater.

MTCW
D

USSR
November 16, 2006, 08:17 AM
With bottle-necked rifle cartridges, to maintain a bullet securely in the case, use neck tension rather than crimping. The only exception to this may be a lever gun with an under the barrel magazine.

Don

GRIZ22
November 16, 2006, 10:42 AM
I reload all the calibers you mention. Crimping also may or not provide more uniform powder ignition depending on the powder and the particular rifle. The only way to know for sure is to chronograph your loads. A chrono can be purchased for less than $100. Chrono the same load with and without. See what gives you more consistent velocities. Sometimes it makes a difference, good or bad: sometimes it doesn't make any difference.

dfaugh
November 16, 2006, 10:51 AM
May be helpful sometimes. My buddy and I were working medium-light to medium-hot loads in 8x57. We were getting alot of soot on top portion of the fired cartridges, which we interpreted to indicate the case wasn't expanding to fill the chmber. We duplicated the same loads, with a light crimp, and got much better/consistant results. Obviously this raised pressures, but we weren't anywhere near max loads, so it worked out great. YMMV of course.

ocabj
November 16, 2006, 10:59 AM
Crimping does not affect neck tension. The actual sizing process does. If you want to control neck tension, use a bushing style sizer. Redding and Hornady both make one. I believe RCBS recently came out with one.

Crimping for semi auto gas rifles is pretty much not necessary. Granted, there's probably going to be the 1% of 1% of 1% chance that you get a bullet set back on a cartridge due to the recoil of a rifle, but that's going to be attributed to another fault.

I don't about revolvers, but in a rifle, you should never crimp if the bullet does not have a cannelure.

The Bushmaster
November 16, 2006, 11:18 AM
The only rifle case that I crimp is .30-30 using a Lee FCD for obvious reasons.

As far as crimping handgun cases it does raise the pressures a bit. Using some "hard to burn" powders it helps.

Lennyjoe
November 16, 2006, 12:44 PM
Loads I crimp;

.44 mag (roll crimp)
.223 for the AR (light crimp only)

Other loads worth mentioning;
10MM and .45 ACP I use a Lee Factory crimp die and its a very light crimp to bring back the uniformity in the case mouth.

I do not crimp 30-06 rounds.

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