How a M4 Carbine Works

Wikipedia: The M4 carbine is a 5.56×45mm NATO, gas-operated,[b] magazine-fed, carbine developed in the United States during the 1980s. It is a shortened version of the M16A2 assault rifle.

The M4 is extensively used by the United States Armed Forces, with decisions to largely replace the M16 rifle in United States Army (starting 2010) and United States Marine Corps (USMC) (starting 2016) combat units as the primary infantry weapon and service rifle. The M4 has been adopted by over 60 countries worldwide, and has been described as "one of the defining firearms of the 21st century".

Since its adoption in 1994,[11] the M4 has undergone over 90 modifications to improve the weapon's ergonomics and modularity, including: the M4A1, which strengthened the barrel and removed the burst-fire option; the SOPMOD, an accessory kit containing optical attachments; and the underbarrel M203 grenade launcher.

In April 2022, the U.S. Army selected the SIG MCX SPEAR as the winner of the Next Generation Squad Weapon Program to replace the M16/M4. The rifle is designated XM5.

Type Assault rifle
Carbine
Place of origin United States
Service history
In service 1994–present
Used by See Users below
Wars See Conflicts below
Production history
Designed 1982–1993
Manufacturer See Manufacturers below
Unit cost $700 (avg. cost)[1]
Produced 1987–present[2]
No. built 500,000[3]
Variants M4A1
Mark 18 Mod 0 CQBR
Specifications
Mass 6.43 lb (2.92 kg) empty[4]
7.75 lb (3.52 kg) with 30 rounds and sling
Length 33 in (838 mm) (stock extended)
29.75 in (756 mm) (stock retracted)
Barrel length 14.5 in (368 mm)
Cartridge 5.56×45mm NATO
Caliber 5.56 mm (.223 in)
Action Gas-operated, closed rotating bolt, Stoner expanding gas
Rate of fire 700–950 round/min cyclic[5]
Muzzle velocity 2,970 ft/s (910 m/s) (M855A1 round)[6]

2,887 ft/s (880 m/s) (M855 round)
2,986 ft/s (910 m/s) (M193 round)
Effective firing range 500 m (550 yd)[7]
Feed system 30-round box magazine or other STANAG magazines.[a]
Sights Iron sights or various optics.