I have 5.56 (.223), 300 BLK, 7.62X39, all in carbine and pistol length, .308 in 22", .22LR, and a.22 Mag on order. The AR platform is so versatile it is truly a fun piece. I have toyed with some larger calibers but for right now I think I am going to stay where I am. Maybe a pistol caliber, but...