The May 1967 "Colt's Ink" newsletter announced that he had won a national competition for his selection and treatment of materials in the design.

The newsletter stated in part, "In only 47 days, he wrote the specifications, designed the launcher, drew all the original prints, and had a working model built."

In July 1966 the US Government contracted Colt Firearms to provide nearly 20,000 XM-148s with the weapon arriving in South Vietnam in December 1966.

The launcher's barrel could slide forward to accept a single 40 mm round into the breech.

It differed from the later model by featuring an external cocking handle and an extended trigger that allowed the weapon to be fired without removing the hand from the rifle's pistol grip.