developed an all-steel water jacket that went into production around 1943; this was stronger than the earlier brass-capped jackets. These steel components were interchangeable with the earlier brass ones to allow for repair of worn or damaged water jacket components. Other changes were implemented, some during the war, but not all M1917s received these updates. Beginning in 1938, the pivot in the top cover was replaced with a new one that would become standard on all M1919-series guns. While the World War I–pattern top cover hinge pin appears to have been retained on most converted M1917s, the later-production M1917A1s had a positive locking top cover hinge pin that allowed the top cover to remain open, lessening the chance of it dropping closed on one's hands while working on the gun—this became the standard on all M1919-series guns. M1918 Air-cooled aircraft version of the M1917. Developed during the First World War, the M1918 arrived too late, but became the dominant weapon of its type in US service until the development of the M1919. It features a heavier barrel, but lighter barrel jacket as compared to the M1917. A sub-variant, the M1918M1, was developed as a flexible version of the fixed M1918. International variants & designations The M1917 pattern has been used in countries the world over in a variety of forms. In certain cases a new designation was applied by the user nation. FN30 From 1930, Belgian Fabrique Nationale produced air-cooled and water-cooled versions of the M1917, chambered in various calibers for domestic and export use. Ksp m/14-29 and ksp m/36 Kulspruta m/14-29 was the Swedish designation for the licensed M1917A1, produced by Carl Gustafs Gevärsfaktori in Eskilstuna, for infantry support. The main differences was that it was chambered in the standard caliber 6.5×55mm, had spade-grips and used the cooling jacket and tripod of the m/14 (Schwarzlose) tripod, the machine gun the Ksp m/14-29 replaced. The reason for adoption of the Browning was cost: 50 machine guns using the Browning mechanism could be made for the same price as 30 Schwarzlose, which was discovered during the manufacture of Kulspruta m/22. The 6.5mm bullet was found to be too light for long-range fire support and anti-aircraft use, so in 1932 the heavier 8×63mm patron m/32 cartridge was developed. As this resulted in a heavier recoil, a spring-loaded cradle replaced the backplate with a heavily spring-loaded buffer that acted as an extension of