M4 Carbine

The M4 carbine is a family of firearms tracing its lineage back to earlier carbine versions of the M16, all based on the original AR-15 made by ArmaLite. It is a shorter and lighter version of the M16A2 assoult rifle, with 80% parts commonality with the M16A2. The M4 has selective fire options including semi-aoutomatic and three-round burst (like the M16A2), while the M4A1 has a "full auto" option in place of the three-round burst.