Yesterday we took a look at the internals of Ruger's select-fire AC-556, and today we have it out at the range. The main question for me was, how does it compare to the M16/AR-15? And the answer is, not all that well. The AR is definitely a softer shooting platform in full auto. The AC-556, despite being basically the same weight and using the same cartridge, jumps around a lot more. The reason is clear in the slow-motion footage; the bolt is slamming into the back of the receiver on each shot.