The M4/M4A1 5.56mm Carbine is a lightweight ... durability, and high-temp/low-temp tests. The Army saved nearly $2 million as a result of the early completion of the competition.

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 ...