Welcome to the Colorado AR-15 Shooters Club Discussion Forums.
Originally Posted by hurley842002 You can shoot 55 grains just fine +1. Generally speaking, the 1:9 is optimal for 55 gr., the 1:7 for the 62 gr. but both barrel twist rates should present them selves well with a spectrum of bullet weights. The tighter the twist, the heavier the bullet.
Forum Rules