If this has been covered befor, I apologize. I have reloading experience but have never loaded for a semiauto. I have a BAR in .308 Winchester I would like to try reloading for.
1. Do I need to crimp?
2. If so do I need a bullet with a cannelure?
3. If I have to crimp, can I use a bullet without
a cannelure and the Lee factory crimp die?
I am going to try IMR 4064 and have read the threads on the right burning rate and timming of the action. Thanks for the help and anything else you would care to offer.

It's usually recommended to crimp for semiautos as the forceful operation of the action could push a bullet back into the case (or conversely, act like an inertia bullet puller as it slams home into the chamber and seat the bullet out against the lands) without a crimp.

The Lee Factory Crimp Die doesn't need a cannelured bullet. It'll crimp right into the jacket, making its own cannelure.

I've reloaded for AR15,AR10,M14,and remington 742.
I've never crimped.
Crimping may or may not bring on accuracy problems.
Some would disagree and have had good results.
with a die that sets proper neck tension,in a non military environment, it isn't necessary IMO.
Tubular magazines,and very hard recoiling rifles need crimped rounds, not sporting or target auto's.
Applying fireproof gel.
Covey

NO! You don't need to crimp for an auto, I never crimped for my 7400 6mmRem., they(bullets)never moved under recoil, noticing upon unloading after shooting at a deer, the fellas I reloaded for also had the Rem. autos and never had a problem either, my dad included, although, If you have a callelure, it won't hurt to crimp it slightly, but not necessary. Jay

Jay Gorski
I removed the decapping rod from my 308 sizing die. I decap on a separate press with a Lee universal decapping die, to keep the crud out of my Forster Co-Ax then I resize the case. Clean over night in the tumbler to remove sizing lube. Then I use a Lyman M-die to expand the neck. However there's a difference I have taken the expanding mandrel chucked it into a drill and polished the mandrel to a mirror like surface and reduced the diameter a RCH. The case neck grips the bullet tightly without crimping.
Jim

I had a BAR in .308, and did not crimp ammo for it! As a matter of fact, I used the same ammo in it that I had made for my pre-64 M70 Featherweight in .308, and used the same tools to load for it - RCBS plain ol' .308 dies, no small-base, no nuthin"!! Never a problem!