Recoilless guns/rifles get their categorization from their inherent ability to counter some of the violent recoil effects related to the firing action by allowing the escape of the produced propellant gasses of the projectile, this usually through a venting system of some sort at the rear of the weapon. The first recoilless guns were used experimentally during World War 1 (1914-1918) as Zeppelin busters and anti-submarine weapons while more purposeful developments were encountered throughout the interwar years with the intent to use these systems as dedicated tank-killing implements and "bunker-buster" solutions. However, more reliance was eventually placed on the anti-material rifle line which, for the British Army, became the storied Boys .55 Anti-Tank Rifle.
As the war across Africa, Europe and the Pacific progressed, the anti-tank rifle began to lose much of its potency as enemy armor continued to offer greater protection through subsequent designs. Engineers, such as Sir Dennis Burney (1888-1968), saw the need and moved to develop proper counters to the new threats. He began work on a recoilless rifle design that was eventually adopted by the British Army as the "Ordnance, RCL, 3.45in Mk 1". A promising venture, the weapon was too late into service to see combat exposure during World War 2 (1939-1945). It was expected that the new weapon could at least help with the Allied initiative in the Far East.
Manufacture of the RCL fell to the Broadway Trust Company. It was a 75lb, shoulder-fired instrument with a tube length of 5 feet, 8 inches. The caliber was 88mm (8.8cm) and the projectile exited at 180 meters per second with an effective firing range of up to 1,000 yards. The 16.25lb shell (Cartridge RCL, 3.45in WB "Wallbuster") relied on a High-Explosive Squad head (HESH) warhead to provide the necessary penetration at range and this compensated for the rather low muzzle velocity in turn. The propellant charge was 11.13lbs of cordite and the warhead contained a plastic explosive filling. As a shoulder-fired weapon, it was relatively man-portable with near-complete freedom for the operator to engage from cover or in "stop-and-pop" actions. The recoil action was aided by perforations aft of the breech to which the propellant gasses leaked. In this way, much of the recoil caused by the exiting projectile was countered to produce a more stable firing platform.
The RCL showcased inadequate wear at its breech section which unfortunately delayed its service entry. In the grand scope of its existence, the RCL went on to leave a grander influence on succeeding British anti-tank designs such as the L6 "WOMBAT" of the 1950s, a truer recoilless rifle design which saw considerable service during the Cold War years.