Bullet weight will have an influence on selecting the correct powder.

Just this week I worked on load development for a member here shooting 69gr SMKs. IMR 4895 is what he had to work with, so while certainly not my first choice we did manage to get 1/2 MOA (@200 yards) with a muzzle velocity of ~2880 FPS from his 20" barrel.

Primers. Remember that the AR has a floating firing pin. Thus the harder the primer the better. CCI makes a "NATO" primer and as surprising as it may sound WOLF makes an excellent hard primer in small rifle.

With that said . . . . I've noticed a significant dent in the primer when I loaded some test rounds using Winchester small rifle primers. I pulled the bullets, saved the powder, and threw the cases away. Slamfire is a bad thing if the bolt is unlocked when it happens.