.223 & .30 carbine; crimp or not to crimp???

[Frog123]

When reloading for the above calibers do I need to crimp either? I'm shooting both from military magazines. I have concerns about bullets becomming dislodged during recoil while in the magazine or having their seating depth change entering the chamber during cycling...




Frog :?

[John Traveler]

You normally can crimp only on bullets with a cannelure (knurled crimping groove).  .30 US Carbine bullets don't have any.  Plus, the cartridges headspaces on the case mouth, like the .45 ACP and 9mm Luger.  You don't crimp on any of these cases, but you DO carefully straighten out the case belling-mouth during final bullet seating.  You can do this carefully using the sizing die.  Only a touch... just enough to remove the flare.

On the .223, a light crimp is a good idea.  You can do this on military bullets with the cannelure, but not on smooth bullets.

Military production ammo uses a case mouth/bullet sealant besides a crimp to hold the bullet in place.  A nice side effect is that it also waterproofs the case/bullet joint.  Try using asphaltum (common tar thinned with solvent.  I've sucessfully used chips of roofing tar thinned with lighter fluid or laquer thinner and applied with a Q-Tip cotton swab.  Dry a few minutes before seating bullets.

You are correct that bullets can push in too deep on feeding impacts in the magazine or feed ramps.  MIL-SPEC ammon aviods this by increasing bullet pull (crimp and sealant).  A relatively easy way to do this on your reloads is to polish down the expander ball to make for tighter bullet-seating fit.

[securitysix]

When reloading for the above calibers do I need to crimp either? I'm shooting both from military magazines. I have concerns about bullets becomming dislodged during recoil while in the magazine or having their seating depth change entering the chamber during cycling...




Frog :?

What actually prevents bullet setback is not a crimp, but neck tension.  If the case is properly sized, you will not get any setback.  

Now, the bullet moving forward under recoil is another story all together.  A roll crimp is usually used to stop this, and will work on .223 with cannelured bullets.  

On .30 Carbine, .45 ACP, and 9mm, a taper crimp is used, and will probably not do much to prevent bullet jump, but that's not often an issue.  The taper crimp is used to get rid of the flare/bell from the case mouth.

[kciH]

Frog,
when loading for the .223 you should not experience any bullet setback if you case necks are properly sized.  If you're using the 55gr FMJ, you can crimp the case, but don't overdo it, you can actually decrease neck tension if you crimp improperly.  With the 68+gr bullets that work best in my HBAR with the 1-7" twist, there is no way the bullets are going to get seated deeper unless they really take a severe pounding because there is no room in the case and the powder is compressed in most loads.  If you are having problems with bullet setback, you can use the Lee Factory Crimp die and it should solve any problems you may be having.

If you're in doubt about having setback problems, it's easy to check it.  Let your bolt feed the round off the magazine and eject it.  Measure your COL and compare to the measurement before the round was chambered.  Do this with a full magazine, not just one round.  I know you know this, but I'm gonna say it anyway, DO NOT do this in your reloading room!  The only safe place to do this is at a range with the muzzle pointed downrange at all times, unless you have a bullet trap in your house.