De Lisle carbine

The De Lisle carbine is a converted Short Magazine Lee–Enfield Mk III* rather than a rifle designed from a blank sheet: its receiver and bolt were reworked to feed .45 ACP, its barrel is a modified Thompson submachine gun barrel, and its magazine housing was built to take a reshaped M1911 pistol magazine. William Godfray de Lisle, an Air Ministry engineer, built the first prototype in .22 calibre as a private venture and tested it on small game near his home; a later 9mm version failed, and the .45 ACP conversion that followed became the design that entered limited production. De Lisle chose .45 ACP specifically because typical loadings of it travel at a subsonic speed, meaning the carbine could use ordinary ammunition without the bullet itself producing a sonic crack; a rifle round travelling above the speed of sound does, regardless of any suppressor fitted to the barrel.

The carbine’s defining feature is a suppressor built as an integral part of the weapon rather than an add-on: a two-inch-diameter tube runs from behind the barrel to well past the muzzle, more than half the gun’s overall length, giving the expanding propellant gas a large volume to lose pressure in before it reaches open air. The Thompson barrel was drilled with ports along its length to bleed gas into this volume progressively rather than all at once. Official wartime testing recorded the weapon at 85.5 decibels when fired, and its manual bolt action meant a user did not have to work the action and produce the noise of cycling unless another shot was needed immediately; a semi-automatic design would have cycled regardless.

Ford Dagenham hand-built an initial batch of 17 for the Combined Operations units that requested it, after which the Sterling Armaments Company took an order for 500 in 1944 but delivered only around 130. A small number of examples with a folding stock borrowed from the Sterling submachine gun were also built for airborne troops. The carbine saw use with British Commandos and the Special Operations Executive during the Second World War, and later with British and Commonwealth forces during the Korean War and the Malayan Emergency.

No clickable primary source states the carbine’s overall length, mass or barrel length independently of the print sources (Peterson’s Standard Catalog of Military Firearms and David Rome’s 1984 history) that Wikipedia cites for them, so those figures are recorded here as estimated rather than verified. No source gives a rifling twist rate, and cyclic rate is not recorded because the De Lisle is a manually operated bolt-action arm rather than a self-loading one.