the use of flashless propellant for night operations. The naval designation was QF 6-Pounder Mk IIA; nearly 600 of these weapons were made. The Molins autoloader was also deployed on a small number of Royal Air Force de Havilland Mosquitos of Coastal Command, which were referred to as the "Tsetse" (after the Tsetse fly). Officially the QF 6-pdr Class M Mark I with Auto Loader Mk III, it was based on the long-barrelled (50 calibre) gun. It was fully automatic, with a cyclic rate of fire of about 55 rounds per minute with 21 rounds carried. It was intended for use against U-boats and fired solid shot that could penetrate their hulls through of water from 1,400 m. The weapon was used to sink a U-boat and, on one occasion to shoot down a Junkers 88 aircraft during an attack on IJN submarine I-29 off Cape Penas. It was replaced in 1943 by the more versatile but less accurate RP-3 3-inch Rocket Projectile. US service In spring 1943, following the experience of the North African Campaign, the Infantry branch of the US Army recognised the need to field a heavier antitank gun than the 37 mm M3. The Ordnance QF 6-pounder was introduced into US service as the 57mm M1, following standard US nomenclature. The introduction was made in the face of objections by the US Army Infantry Board, which believed it to be too heavy. The Ordnance Board, on the other hand, felt that a more powerful weapon should be introduced; the Airborne and Cavalry rejected it. According to the Table of Organisation and Equipment (TO&E) from 26 May 1943, a regimental antitank company included nine 57 mm guns and each battalion had an antitank platoon with three guns, giving a total of 18 guns per regiment. Dodge WC-62/WC-63 6×6 1½ ton trucks were issued as artillery tractors in place of the 3/4 ton truck used with its predecessor the 37mm. Because of the unexpected adoption into service, the only ammunition type in production in the US was the AP ammunition. By mid-1944, the M1 was the standard antitank gun of the US infantry in the Western Front and outnumbered the M3 in Italy. Preparation for the D-Day invasion of Normandy highlighted an additional need. The Airborne Command had rejected the 57 mm M1 in the summer of 1943, claiming that it was unfit for airlanding by glider due