Case crimp on 308 Win.

[mcxring]

I just Bought a AR-10 308 Bushmaster, awesome gun, I reload my AR -15 .223 with no crimp, and don't have any problems, since not crimping, accuracy has improved, the .308 being a much heavier bullet and load, is a crimp required, if yes, what kind of crimp. Thnx Mike

 

[markm87]

Depends on a lot of things... mostly neck tension. If you're getting solid neck tension, you can feed the ammo in an auto loader. I don't crimp .308 for the gas gun we're running.

Crimping actually helps my .223 ammo out. I just blow through mixed brass. And since the ammo will be fired in bolt and gas guns, I put a light factory crimp on the ammo. Seems to help give me consisnent neck tension. SMKs will shoot 1/4 MOA on good days.

 

[amlevin]

I was playing around for a while with the crimp/no crimp idea on my .308 loads. They are all shot in a bolt gun and while there was not "need", I went ahead and ran some loads through my Lee FCD.

I measured run-out prior and post crimping. I set the die so it just contacted the case neck with a little pressure, not really a crimp in the traditional sense.

All I gained from the experiment was that some of the cartridges with higher run-out had it reduced. Some went from .002" to .001". Didn't notice any difference on the targets so the die is on "Standby" duty.

 

[fr3db3ar]

No crimp required on mine. When I shoot 150 SGK the ones in the mag will get a flattened nose as opposed to pushing back into the case.

 

[Glenn Powell]

I don't have a 308, but my 300 loves a crimp on hornady interlocks, just thought I would give it a try and it made a huge difference. Ya never know till ya try. Some say it gives a better or more consistent powder burn, and more time for the powder to gas up.

 

[amlevin]

Some say it gives a better or more consistent powder burn, and more time for the powder to gas up.

At least Richard Lee says so. According to his "Second Edition" a positive crimp affects the ignition, pressure, velocity, and accuracy of a round. He also says that there should be 100# of "bullet pull" so the bullet starts to move as the chamber pressure passes 1338 PSI (for a .30 cal bullet). It's his opinion that this 100# bullet pull can't be reached without a crimp.

An interesting view and I'm sure there are lots of others on this subject.