M4 carbine

The M4 carbine is a shorter and lighter variant of the M16A2 assault rifle. The M4 is a 5.56×45mm NATO, air-cooled, Stoner expanding gas system, gas-operated, magazine-fed carbine. It has a 14.5 in barrel and a telescoping stock. Wikipedia

Barrel length: 14.5″

Caliber: 5.56 mm

Length: 33 in (838 mm) (stock extended); 29.75 in (756 mm) (stock retracted)

In service: 1994–present

Unit cost: $700 (avg. cost)

Muzzle velocity: 2,970 ft/s (910 m/s) (M855A1 round)