I think the rifle in question was the Johnson, which operated by short recoil, meaning that the gun remained locked for less than the length of the cartridge. There was a lot of argument in the mid and late 1930's and early 1940's over the adoption of a semi-auto rifle for the U.S. military.
The first competitor to the Garand rifle was the Pedersen, which used a toggle system that was not really a locked bolt at all, but which used mechanical disadvantage to keep the gun closed until pressure dropped.
The second major competitor was the Johnson. Even though the Garand had been adopted as the M1 rifle in 1936, Johnson believed his rifle was better, and it had some advantages. This led to a lot of bitterness between Johnson (a Marine reserve officer with no combat experience) and the Army Ordnance department, with charges of rigged tests, favoritism, etc. FWIW, I have both rifles and believe the M1 is clearly superior to the Johnson, though the superiority may not have been as evident in 1941.
Some Johnson rifles were used in combat in the Pacific by Marines and by soldiers of the Netherlands East Indies.
Other recoil operated rifles have been the Remington 8 and 81, which were long recoil operated. There have been others, but these are the best known. I think the best known long recoil operated guns are the Browning Auto 5 shotgun and its variations and copies.
Almost all high power semi-auto pistols operate by short recoil; at least two, the Frommer Stop and Frommer Baby, were long recoil operated.
Jim
