Much of the history behind the suppressed M1 carbine remains unclear. Great Britain’s Royal Small Arms Factory apparently developed this quiet version of the iconic M1 for the U.S. Office of Strategic Service and the British Special Operations Executive, probably between 1943 and 1945.
Based on standard receivers built by General Motors’ Inland Division, the carbines had a shortened 10- or 11-inch barrel rather than the normal 18-inch barrel.
The weapon included a 13- or 17-inch-long suppressor that screwed onto the receiver. The carbine weighed approximately 1.75 pounds more than the standard, unsuppressed M1.
The design had a ported barrel with seven, .125-inch-diameter holes enclosed by the suppressor, which itself contained 10 metal back-baffles that surrounded the barrel.
The suppressor had a small expansion chamber in front of the muzzle, followed by 11 cone-baffles at the front of the suppressor housing.
In order to further mitigate the carbine’s report, the weapon boasted a specialized, subsonic .30-caliber cartridge. As a result, the shooter had to manually cycle the suppressed M1 after each shot, unlike with the standard carbine.
The experimental section at the Royal Small Arms Factory at Enfield built at least six examples, although it remains unclear if any of the carbines ever saw action. A 1968 Frankford Arsenal report notes that the weapon sounded “like a sharp hand clap followed by a distinct hissing sound,” with the weapon’s report peaking at 122 decibels.
The report concludes that because “of its bulkiness, manual feeding and not too impressive acoustical performance, it is doubtful if the weapon was widely utilized.”
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