I've loaded I don't know how many thousands of 223s I loaded over the last 40 years and I have yet to crimp, or need to put a crimp on a 223 bullet.
As far as what's the best bullet for your gun, you have to know the twist, faster twist will shoot lighther bullets better then a slower twist will shoot heavy bullets.
Best thing, pick the weight (actually length) that matches your twist, then buy as many different kinds as possible and find one that fits your gun.
I could tell you what works in my guns, but it would mean nothing, you're not loading for my guns.
CPT USAR Ret
USAMU Sniper School Oct '78
Distinguished Rifle Badge 1071