An American single-shot, muzzle-loading 40mmunderbarrel grenade launcher. It was designed to replace the M79, which was a stand-alone weapon. The under-barrel design gave soldiers the advantage of having quicker switch of both rifle and grenade launcher, making them more adaptable in combat. The M203 was originally designed designed for the M16 and M4 Carbine but can be fitted to many other rifles without modification.