M16 cyclic ROF is 800 rounds per minute (http://www.globalsecurity.org/military/systems/ground/m16-specs.htm), which gives about 13 rounds per second. They also give their speed as 120,000 rpm, not rps. Still, 2000 rounds per second at better than Mach 2 is going to make a bitch of a noise.

I agree that "recoilless" likely means "low-jerk" in this case: Newton is still upset over that word.

Power, ammunition supply, frictional heat... there are a few "issues."