The Boys anti-tank rifle (officially Rifle, Anti-Tank, .55in, Boys, and sometimes incorrectly spelled "Boyes"), is a British anti-tank rifle used during the Second World War. It was often nicknamed the "elephant gun" by its users due to its size and large bore. There were three main versions of the Boys: an early model (Mark I) which had a circular muzzle brake and T-shaped monopod, built primarily at BSA in England; a later model (Mk I*) built primarily at the John Inglis and Company in Toronto, Canada, that had a rectangular muzzle brake and a V shaped bipod; and a third model made for airborne forces with a 30-inch (762 mm) barrel and no muzzle brake. There were also different cartridges, with a later version offering better penetration. Although adequate against light tanks and tankettes in the early part of the war, the Boys was ineffective against heavier armour and was phased out in favour of the PIAT hollow charge weapon mid-war. Design and development The firearm was developed by Captain Henry C. Boys, Assistant Superintendent of Design—1885-1937, who was a member of the British Small Arms Committee and a designer at the Royal Small Arms Factory, Enfield. It was initially called Stanchion but was renamed after Boys when he died a few days before the rifle was approved for service in November 1937. A bolt action rifle fed from a five-shot magazine, the weapon was large and heavy with a bipod at the front and a separate grip below the padded butt. In order to combat the recoil caused by the large round, a muzzle brake was fitted on the barrel while the receiver was allowed to slide along the frame with a shock absorber attached to the rear of the rifle. The Boys had been designed with numerous small narrow-slotted screws of soft steel set very tight into the body of the weapon and its repair and maintenance proved difficult. The .55 Boys cartridge was an adaptation of the .50 BMG with a belt added firing a bullet. At its introduction, the weapon was effective on light armour thick at . Two main service loads were used during the Second World War: The W Mark 1 a AP projectile fired at , and the W Mark 2 ammunition, AP at . The W Mark 1 could penetrate of armour at , about the thickness used on the frontal armour