While the Special Purpose Infantry Weapon (SPIW) program failed to produce any successful rifles, it did become clear that the area-effect aspect of its requirements did have merit. This was spun off as its own program to develop a 40mm under barrel grenade launcher for the M16 rifle. Of the initial entrants, (Philco/Ford, AAI, and Colt), Colt’s CGL-4 was the most promising. It was moved quickly through development and 10,500 were ordered in January 1966 as the XM-148. Field reports quickly turned sour, though, and in May of 1967 the XM-148 was ordered out of combat use, to be replaced with the M79 grenade launcher. The idea was sound, but the execution needed improvement – which would come in the form of the M203 launcher instead.