Since their formation in the 1960s, the Navy’s SEALs have been on a quest for more firepower. The elite commandos have been especially interested in bigger grenade launchers.

The sailing branch formed the Sea, Air and Land Teams in 1962. These “unconventional warfare” units—what we call Special Operations Forces today—quickly became known for their vast arsenals of experimental weapons.

By the end of the decade, naval commandos had tested new lightweight machine guns, automatic shotguns and silenced weapons. The specialized teams were also interested in grenade launchers.

The U.S. Army had led the way with a crude but effective weapon called the M-79. The launcher fired a 40-millimeter projectile farther than an infantryman could toss a hand grenade.

But the M-79 could only fire one shot before it had to be reloaded. The SEALs wanted a weapon that used the explosive ammunition and could fire multiple rounds in a row.

A T-148E1 grenade launcher. Army photo

In the late 1950s, the Army had tried to incorporate a three-round sliding magazine into the existing design. The ground combat branch’s Special Forces tested some of these launchers, called the T-148, in Vietnam.

SEAL Team One also got its hands on one of these prototypes, according to an article by noted SEAL historian Kevin Dockery. The unit assumed the open-ended magazine would quickly fill up with debris and jam—and never used it in combat.

Disappointed by the Army’s offering, the commandos turned to their own service for new concepts. The sailing branch created the Special Operations Branch at the Naval Weapons Center in China Lake, California specifically to address these requirements.

China Lake created two different multi-shot grenade launcher designs during the 1960s. One weapon was designed to be attached to a standard M-16 rifle, while the other resembled a large shotgun.