M4A1

The M4 carbine is a shorter and lighter variant of the M16A2 assault rifle. The M4 is a 5.56×45mm NATO, air-cooled, direct impingement gas-operated, magazine-fed carbine. It has a 14.5 in (370 mm) barrel and a telescoping stock.The M4 is capable of firing in semi-automatic and three-round burst (like the M16A2 and M16A4), while the M4A1 is capable of firing in semi-auto and full automatic (like the M16A1 and M16A3). The M4A1 carbine is a fully automatic variant of the basic M4 carbine intended for special operations use. The M4A1 has a "S-1-F" (safe/semi-automatic/fully automatic) trigger g...