Ordnance Notes -- by Bob Stoner GMCM (SW) Ret

Ordnance Notes -- by Bob Stoner GMCM (SW) Ret.

Colt XM148 40mm Grenade Launcher

A Colt XM148 grenade launcher attached to a Colt XM177E2 submachine gun. Note that the lower hand guard is not used when the launcher is attached to the barrel. Colt also made a special round, ventilated metal hand guard to replace the triangular hand guards of the M16 or M16A1 rifle. The cumbersome sight for the launcher is just visible behind the launcher itself. In use, the grenade sight was removed as too complex and too cumbersome. (Photo: Colt Firearms)

The Colt XM148 was the first attempt to put a 40mm grenade launcher on the M16 rifle. This experiment grew out of the Army's "wonder weapon" of the 1960's era: SPIW -- Special Purpose Individual Weapon. The SPIW was envisioned as a "point fire" weapon that shot bursts of 13-grain flechette projectiles or an "area fire" weapon that shot 40mm grenades – similar to the M79.

The SPIW went through at least three generations before it became the SBR -- Serial Bullet Rifle -- and then faded away in the mid-1970s. However, the idea of a grenade launcher that attached to the infantry rifle caught on.

Colt's Firearms was the first out of the box with their XM148 launcher. The barrel of the launcher telescoped forward from the receiver of the weapon to load. The barrel latch was a small pistol shaped grip that hinged forward to open the breech. There was a long combination trigger/safety rod attached to the receiver. The hook (trigger) attached to the end of the rod pivoted UP for SAFE and DOWN for FIRE.

Left and right side photos of a Colt XM148 grenade launcher attached to a Colt XM16E1 rifle. The original triangular plastic handguards could not be used when the XM148 was attached to the rifle barrel and they were replaced by a stamped steel cover. The complex grenade sight attached to left side of the rifle and was used for direct fire. In use, the grenade sight was often removed as too complex and too cumbersome. The lower photo shows the controls for the launcher. The long rod with the L-shaped handle (below the trigger guard) is the trigger that fires the launcher (shown rotated to firing position). The other L-shaped handle in front of it is the cocking handle. The small pistol grip has a latch on the back to open the breech of the launcher for loading or extracting and ejecting fired cases. (Photos: U.S. Army)

When fitted to the rifle, the triangular plastic hand guards of the M16 or M16A1 were replaced by a round, ventilated sheet metal stamping. When attached to the XM177E2 submachine guns, the upper round hand guard was used and the lower hand guard was left off to attach the XM148 to the shorter barrel. A dial sight (similar to an enlarged version of the M15 rifle grenade sight) was attached to the left side of the launcher for direct or indirect fire.

Several hundred XM148 launchers were manufactured and evaluated from 1965 to 1967 when it was rejected for the XM203 launcher designed by Aircraft Armaments, Inc. (AAI). The photo shows an XM148 launcher attached to the M177E2 5.56mm submachine gun (aka CAR-15). Most SEAL grenadiers were still using the XM148 launcher at SEA FLOAT/SOLID ANCHOR. MST-2 units preferred the M79.

A photo of an early Colt XM148 grenade launcher. The attachment lugs for mounting the launcher on the rifle are clearly shown. The mushroom-shaped knob is used to cock the launcher in this early version. The trigger and its connecting rod are not shown in this photo. The pistol grip latch is clearly shown, but does not have the release lever added later. (Photo: U.S. Army)

A Colt XM148 grenade launcher attached to a Colt XM177E2 submachine gun carried by an Australian SAS [Special Air Service] trooper operating with Navy SEALs in Viet Nam. He is dressed in both Australian and American equipment. Both SEAL and SAS operators used Levi jeans on operations because of their toughness. The trousers are bloused and tied-off to prevent the entry of leaches. (Photo: U.S. Navy)