when did the army switch to the m4
M4 carbine In 1984, the first model was made, and it was tested in May 1985. The first model have a Upper A1 Sight, and was given a shorter 11.5-barrel, but later it was giving a longer 14.5-inch barrel for the bayonet and the M203 Grenade Launcher. The second model was made in May 1986, and it was tested from May 1986 though May 1987, at the time it have a A2 Upper Sight, and it have the M16A2's 1:7Â inch rifle twist, to use the heavier 62-grain M855 rounds. The extended barrel improved the XM4's ballistics, reduced muzzle blast and gave the XM4 the ability to mount a bayonet and the M203 grenade launcher. The XM4 was also given the cartridge deflector, as well as other minor refinements.[citation needed] In May 1991, the XM4 was renamed to the M4, and Colt made a manual. In 1994, the U.S. military officially accepted the M4 into service to replace M16A2s in certain roles.[10] The M4 carbine has also replaced most submachine guns and selected handguns in U.S. military service,[10] as it fires more effective rifle ammunition that offers superior stopping power and is better able to penetrate modern body armor.[citation needed]