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Old June 1, 2012, 07:37 PM   #14
Bart B.
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Join Date: February 15, 2009
Posts: 8,927
Wyoredman, any crimp on a round of ammo impairs its accuracy. Period. Go to one of the benchrest forums, register then post a thread asking them about crimping case necks onto bullets.

Crimping adds an uneven indentation all the way around the bullet. Expecially if there's no cannelure groove for the crimp to go in. If your bullets are already very good, well balanced ones, why would one want to make the less balanced by putting an uneven wrinkle all the way around them? Crimping also adds more grip on the bullet that's more uneven than neck tension alone. That increases muzzle velocity spread causing greater vertical shot stringing at the longer ranges.

There's more than enough neck tension on regularly sized 22 caliber botteneck cases that hold bullets very well during recoil. .223's and 5.56's don't have much recoil anyway. Even with 7.62 NATO and 30 caliber in service rifles that don't have crimped in bullets do just fine in semiauto fire with a lot more recoil and much heavier bullets.

Except for match and special sniper ammo, military ammo's got crimped case mouths on bullets with a cannelure groove. They're made that way to survive rough handling from arsenal to the weapon at its firing site. MIL SPEC for 5.56 NATO M193 ammo says "The force required to extract the bullet from the cartridge case shall be not less than 35 pounds." The ammo we loaded for our M16's at the 1971 Nationals had a relase force of about 15 pounds without crimping and none of them got set back from recoil while in the magazine. Nor did they set back from loading in semiauto fire.

Last edited by Bart B.; June 2, 2012 at 03:08 AM.
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