A shortened variant of the M16A2 rifle, the M4 carbine provides ... Compared to the M4 , the M4A1 has full auto capability, a consistent trigger pull, and a slightly heavier barrel.

The four designs featured some improvements over the M16A2, but not enough to justify ... fire depending on the automatic setting. At full auto, it fired 460 rounds per minute, while on three ...

It works with the M4 Carbine, the M249 machine gun, and the H&K and M16A2 rifles. It is suitable for use in most weapons with a 1-in-7 barrel twist. The M855A1 has a copper-jacketed steel core ...