Gun History: Colt XM148 – The First Grenade Launcher Made for the M16
This 40mm launcher was made to be installed under the barrel of an M16, but problems caused it to be pulled from service and replaced.
The M203 40mm grenade launcher slung under an M16 rifle is an iconic sight, giving the gun a distinct profile…it also freed up a grenadier to also be a rifleman. Before the M203, they were relegated to using the M79 grenade launcher and usually carried a pistol in addition. But, did you know that there was an earlier version of the same concept that was issued to troops in Vietnam?
The XM148 was an experimental grenade launcher that also fired 40mm shells and was developed by Colt as the CGL-4.
The XM148 won a national competition in May 1967 and was designed to be installed below the barrel of an M16 to replace the standalone M79.
In July 1966, Colt was contracted by the government to produce about 20,000 of the launchers with the XM148 scheduled to arrive in South Vietnam in December 1966.
They shipped on time, but were pulled from service in 1967 due to a number of problems.
First let’s look at how it worked. The launchers barrel slid forward to open the breech and accept a single 40mm round. It featured an external cocking handle and an extended trigger that allow it to be fired without removing the trigger hand from the rifle’s pistol grip. The trigger was actually a long rod that wrapped around the magazine well and settled right behind it.
That extended trigger caused some accidental discharges when catch on tree branches, gear, or anything else that could overcome the 6 to 11 pound trigger pull weight.
The launcher was also complicated and difficult to break down and reassemble with a lot of small parts that go lost easily in the jungle.
These shortcomings cause the military to pull it from service, though some special forces operators continued to use them, sometimes modified. The U.S. Air Force jet a number of XM148s and were training with the min lieu of the M203 as late as 1989 and some security police units still had them well into the 1990s.
The M203 launcher, which solved all of the aforementioned shortcomings of the XM148, was introduced in 1969. It has a conventional trigger inside a trigger guard that is typically pulled with the support hand while grasping the rifle’s magazine.
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Story by David Maccar