In the mid-1930s, Polish small arms designer
Wawrzyniec Lewandowski was given the task of developing a flexible gun based on the
rkm wz. 28 light machine gun. The desired changes included raising the cyclical rate of fire to 1100 rds/min, replacing the buttstock with a spade grip at the rear of receiver, moving the main spring under barrel and, most importantly, changing the feed system. The gun's original 20 round box magazine was impractical with the gun's high rate of fire. A new feeding mechanism was added as a pack to the standard receiver. It contained a spring-loaded lever, which when cammed by the lock during locking would grab a round from a 91-round pan magazine located above the receiver and force the round into alignment to feed during unlocking. The weapon is the world's only specialised aerial flexible machine gun based closely on the
Browning M1918, or "Browning Automatic Rifle". The wz. 37 was dubbed "Szczeniak" (Polish for "pup") due to its lightness and compactness compared to
Vickers E and Vickers F machine guns it was intended to replace and the "barking" sound it made when shooting. During World War II the wz. 37 was used onboard
PZL.37 Łoś bomber and
LWS-3 Mewa reconnaissance aircraft. This machine gun was also intended as a standard on-board weapon for other aircraft that did not manage to enter service before the outbreak of the war (
PZL.46 Sum,
PZL.48 Lampart,
PZL.49 Miś). ==Users==