76 mm air defense gun M1938 (3-K)

• Name — 76 mm air defense gun M1931 (3-K) • Type — Anti-aircraft gun • Origin — Soviet Union • Is Ranged — yes • Is Artillery — yes • Service — 1932–1977 • Used By — See 76 mm air defense gun M1931 • Wars — * Spanish Civil War • Winter War • World War II • Designer — * Original design: Rheinmetall • Soviet official credit: G. P. Tagunov • Design Date — 1931 • Manufacturer — Red Putilovite plant • Developed Into — 76 mm air defense gun M1938 • Production Date — 1931–1938 • Mass — * Travel: 4820 kg • Combat: 3650 kg • Part Length — * Overall: 4.1 m L/55 • Rifling: 3.37 m L/44.2 • Crew — 10 • Cartridge — Fixed QF 76.2×558mmR • Cartridge Weight — 6.6 kg • Caliber — 76.2 mm • Rate — 10 – 20 rpm • Velocity — 815 m/s • Max Range — 9.3 km AA ceiling • Breech — Semi-automatic vertical sliding-wedge • Recoil — Hydro-pneumatic • Carriage — Two-wheeled carriage with collapsible cruciform outriggers • Elevation — −3° to +82° • Traverse — 360°

Based on the design made by German company Rheinmetall, the configuration of the air defense gun M1931 is similar to the design of the contemporary Vickers 3-inch anti-aircraft guns. The Soviet M1931 had a two-wheeled carriage with collapsible cruciform outriggers. The M1931 was replaced in production in 1938 by the 76 mm air defense gun M1938 which had a four-wheeled dual-axle carriage with two collapsible outriggers. The M1931 and M1938 had nearly identical performance and were gradually replaced by the more powerful 85 mm air defense gun M1939. M1931 guns captured by the Germans were given the designation 7.62 cm Flak M.31(r) and used until they were either worn out or their ammunition supply ran out. A few were rebored to fire German 8.8 cm ammunition and redesignated the 7.62/8.8 cm Flak M.31(r). However, the majority were scrapped in 1944.

A number of M1931 guns were captured by Finland during the Winter War and were employed by them as the 76 ItK/31 ss during World War II. After the war, a number of Finnish guns were converted into light coastal guns (76 ItK 31 Rt, where "Rt" stands for "rannikkotykistö" = coastal artillery) by the addition of a scope site with manual lead mechanism for direct fire against moving surface targets. These guns were still in use as training guns of the coastal artillery into the 1980s.

• Nazi Germany • Finland • Soviet Union • Spanish Republic

• Illustration — AA guns of the 268th Separate Anti-Aircraft Artillery Battalion during the defense of Nikolayev, August 1941