The first successful semiauto rifle submitted to the US War Department was this design by Soren Hansen Bang of Denmark, in 1911. Two examples were sent to Springfield armory for testing, and they made a very positive impression with the staff there. It functioned very well, despite a few faults. In order to meet a weight requirement for the US Army (no heavier than the 1903 Springfield bolt action rifle), it had a very thin barrel, and a hollowed-out stock. This led to rapid overheating, and charring of the wooden furniture.

The rifle used a sliding cap on the muzzle to function Gas released from the muzzle would pull the cap forward, and this force was transmitted through a wire to cam open the rotating bolt and then push it rearward.

Bang presented another gun to the US military in 1927, but it was very similar to his original, and while the original gun had great promise, it was not refined enough for military service. When John Garand began working on a replacement for his early primer-actuated rifle, Ordnance officers urged him develop Bang’s basic principle. He did so, and this led to the early gas-trap Garand rifle.

For more history on the early development of a semiauto military rifle in the US, I recommend Major Julian Hatcher’s excellent work, Hatcher’s Book of the Garand.

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(1927) Bang Model B1 Rifle (English)