M-42 was a 45-mm Soviet light semi-automatic anti-tank gun. Full official name is 45-mm anti-tank gun model 1942 (M-42) (Russian: 45-ìì ïðîòèâîòàíêîâàÿ ïóøêà îáðàçöà 1942 ãîäà (Ì-42)). These guns were used from 1942 until the end of World War II.
The M-42 was developed by the No. 172 Plant in Motovilikha as an upgrade of the 45 mm anti-tank gun M1937 (53-K). The gun received a longer barrel, shells with more powerful cartridges, and a thicker shield (7 mm instead of 4.5 mm), but of hinged construction as a need for reduced profile, requiring the weapon to be serviced by crews while kneeling. Some minor changes were also introduced in order to speed up production.
These guns were used from 1942 until the end of World War II. In 1943, due to its insufficient anti-armor capabilities against new German tanks such as Tiger, Panther and Panzer IV Ausf H, the M-42 was partially replaced in mass production by more powerful 57 mm ZiS-2 anti-tank gun. The M-42 remained in production, however as it was quite effective against lighter vehicles and could pierce the side armour of Panther and Panzer IV Ausf H. Fragmentation shell and canister shot gave the gun some anti-personnel capability.
Mass production of M-42 ceased in mid-1945. The total number of guns produced is 10,843.