U.S. production
The idea of manufacturing the 6 pounder in the U.S. was expressed by the
U.S. Army Ordnance in February 1941. At that time the U.S. Army still favored the
37mm Gun M3 and production was planned solely for
lend lease. The U.S. version, classified as substitute standard under the designation
57 mm Gun M1, was based on the 6 pounder Mk 2, two units of which were received from the UK. However, since there was sufficient lathe capacity the longer barrel could be produced from the start.
[3] Production started early in 1942 and continued until 1945. The M1A1 variant used US "Combat" tyres and wheels. The M1A2 introduced the British practice of free traverse, i.e., the gun could be traversed by the crew pushing and pulling on the breech, instead of solely geared traverse, from September 1942. The M1 was made standard issue in the Spring of 1943.
A more stable carriage was developed but not introduced. Once the 57 mm entered US service a modified towing point design was introduced (the M1A3) but only for US use. Tractors for the M1 include the
Dodge WC-63 11⁄2-Ton 6x6 and the
White Half-Track.
Two-thirds of American production (10,000 pieces) went to US Army Divisions in Europe. About one-third of production (over 4,200 pieces) was delivered to the UK and 400 pieces were sent to Russia through Lend Lease. When the United States re-armed and re-equipped Free French forces for the Normandy landings, their Anti-Tank units received American-made M1s.
Like the British Army, the U.S. Army also experimented with a squeeze bore adaptor (57/40 mm T10), but the program was abandoned. American shell designs and production lagged behind the introduction of the gun once it was accepted for service and so at first only AP shot was available. The HE shell was not available until after the Normandy landings and UK stocks were procured to cover its absence.
Its use by regular US Army front-line units was discontinued in the 1950s.