Karabin maszynowy wz. 37

Karabin maszynowy obserwatora wz.37
Type	aerial, flexible machine gun
Place of origin	Poland
Service history
In service	1937 to 1949
Used by	See Users
Wars	World War II
Production history
Designed	1937
Manufacturer	Państwowa Fabryka Karabinów
Produced	1937 to 1939
Specifications
Weight	7 kg (15 lb) (empty)
Length	1,110 mm (44 in)
Barrel length	611 mm (24.1 in)
Cartridge	8x57mm IS
Caliber	7.9mm
Action	gas operated
Rate of fire	1100 round/min
Muzzle velocity	853 m/s (2,800 ft/s)
Feed system	91 rounds

The karabin maszynowy obserwatora wz.37 (Polish for "observers machine gun") is a Polish version of the Browning wz.1928. It was a flexible machine gun used in the some Polish airplanes in the beginning of World War II.

In mid-1930s Polish small arms designer Wawrzyniec Lewandowski was charged with developing a flexible gun based on Browning wz.1928. The changes included rising theoretical rate of fire to 1100 rds/min, eliminating buttstock, adding spade grip in the rear of receiver, moving the main spring under barrel and most importantly changing the feed system. Keeping the 20 rds box magazine was impossible in the gun firing so fast. The solution was found in developing feeding mechanism, which was added as a pack to standard receiver. It contained a spring-loaded lever, which pressed by the lock during locking would grab a round from 91 rds pan magazine located over receiver and force the round into feed line during unlocking. The weapon is world's only specialised aerial flexible machine gun based closely on M1918. The wz.37 was dubbed "Szczeniak" (Polish for pup) due to its lightness and compactness compared with previously used Vickers E and Vickers F machine guns. The wz.37 was used mostly in Polish PZL.37 Łoś bombers.

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