and selected M9 pistols and M16 rifles. The Army is pursuing a two-phase PIP to keep the M4 carbine inventory strong. Phase I upgrades the Army’s M4s to the Special Forces’ M4A1, while Phase ...

The M4A1, like its predecessor the M16, is based on a gas-operated system with direct impingement, which provides both benefits and certain drawbacks. The M4A1 weighs about 2.7 kg without a ...