WWII Tech Pubs Briefing

Written by
Lawrence Nyveen

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Overview

The Grenade à main offensive modèle 1937 (Offensive Hand Grenade Model 1937, officially abbreviated Gr Ma Of 37 but often erroneously referred to as the Grenade OF) developed from the Grenade F1 modèle 1915 (usually shortened to F1), used by France in World War I and adopted by the U.S. in 1917.

The F1 had the familiar pineapple shape, with longitudinal and transverse grooves in the casing to aid the fragmentation process (not to aid grip, contrary to popular myth).  The French Army continued to use F1s with upgraded ignition mechanisms into World War II.

Unlike its predecessor, the Of 37 was not an anti-personnel fragmentation grenade.  It relied purely on concussive effect to disable opponents.  Its smooth sheet-metal casing did not contribute much to its lethality.  As its name indicates, this weapon was intended for use in attack, generally in close quarters, and was painted gray to further avoid confusing it with Df (defensive) 37 grenades that had the same smooth casings but made from cast iron.  When the Df 37 exploded, the iron would shatter and send shrapnel out in a considerably greater lethal radius than the Of 37.  A mix up would often prove fatal.

The World War II era French grenade’s main improvement over the original F1 was the refinement of the Bouchon-allumeur automatique modèle 1935 (Automatic Plug Igniter Model 1935), commonly known as the mousetrap igniter or Bouchon fuse in anglophone armies, which in World War I introduced the safety lever mechanism familiar to us today. 

In preparation for throwing the grenade, a soldier clasps the safety lever firmly and removes the safety pin.  As long as the soldier holds down the safety lever, the weapon has not been armed and the safety pin can be re-inserted.  Once the lever is released, a spring-loaded firing pin activates the primer.  At that point, only a malfunction will prevent the grenade from exploding.

Like so much other French equipment, large numbers of Of 37s and Df 37s were captured in 1940 and later used by the Germans, who designated them the Eihandgranate (egg hand grenade) 302 (f) and 314 (f), respectively.

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Specifications

Figures are for Gr Ma Of 37.