A great piece of silencer history: the DeLisle Carbine.
The designer was William De Lisle. It was based on a Short, Magazine, Lee-Enfield Mk III* converted to .45 ACP by modifying the receiver, altering the bolt/bolthead, replacing the barrel with a modified Thompson submachine gun barrel, and using modified magazines from the M1911 pistol. The primary feature of the De Lisle was its very effective suppressor which made it very quiet in action – indeed working the bolt to chamber the next round makes a louder noise than firing a round. The De Lisle carbine was used by the British Commandos and special forces, and was accurate to 250 metres.
The De Lisle was made in very limited numbers; 129 were produced during the period of 1942 to 1945 in three variations (Ford Dagenham Prototype, Sterling production and one Airborne prototype). Thompson sub-machine gun barrels were modified to provide the .45 calibre barrel, which was ported to provide a slow release of high pressure gas.
The suppressor, 2 inches in diameter, went all the way from the back of the barrel to well beyond the muzzle (the suppressor makes up half the overall length of the rifle), providing a very large volume of space to contain the gases produced by firing. This large volume was one of the keys to the effectiveness of the suppressor. The Lee-Enfield bolt was modified to feed the .45 ACP rounds, and the Lee-Enfield’s magazine assembly was replaced with a new assembly that held a modified M1911 magazine. Because the cartridge was subsonic, the carbine was extremely quiet, possibly one of the quietest guns ever made.
Write-up c/o Wikipedia.