I don't crimp any rifle shells except for a slight taper crimp on my 30 carbine.
I've loaded thousands upon thousands of 308, 99% for competition in my or others, M1A or issued M14. I never crimped nor have I ever had a problem by not crimping.
Pistols yes, rimmed straight wall with a heavy roll crimp, semis like the 45 ACP, 9mm, 40 cal, I use a taper crimp.
CPT USAR Ret
USAMU Sniper School Oct '78
Distinguished Rifle Badge 1071