During the latter half of the 1930s, the US Cavalry decided to experiment with adapting the .50 caliber Browning M2 heavy machine gun into a bipod-mounted, shoulder-fired configuration. The goal was to devise a variant of the gun that would be more portable and flexible than the standard model with it’s separate tripod. Here is one of the early iterations:
This first version used a pretty much stock early M2 mounted in a spring-loaded soft mount to absorb some of its recoil, and fitted with a large shoulder brace, semiautomatic pistol grip trigger, and hefty bipod. The weapon was also fitted with a T3 prismatic optical sight, the utility of which I would have to question. In a recoiling carriage like this gun has, the optic seems like it would be much more of a hazard to the shooter’s eye on recoil than a helpful sighting aid.
As the experimenting continued, the soft mount was abandoned, and the later versions are actually more akin to normal M2 machine guns with shoulder pads and bipods – longer barrels were also used, probably to help dampen the recoil and blast:
Presumably, the gunner would have used short belts of ammunition with the guns, since they were not capable of full-auto fire. The targets would probably have been basically the same as the obsolete AT rifles used in WWII, and the anti-material rifles used today – light vehicles, structures like radio transmitters, parked aircraft, etc. Not a bad idea, but the M2 was probably not the best way to approach the goal.
Ultimately, the project was abandoned just before the US entered WWII. The reason was that these modified guns actually wound up being heavier to carry, slower to bring into action and required more space to get the same amount of traverse as a standard M2 and tripod. The problem with weight was that the regular M2 broke down into three piece – action, barrel, and tripod. The experimental guns here all used permanently attached bipods, meaning that while they were about 20 pounds lighter overall, they only broke down into two pieces, and the action was heavier than the standard one. With the final version, the heavier of the components weighed in at a rather staggering 77 pounds – imagine the poor grunt who had to add that to his standard loadout. Now, these were intended to be Cavalry weapons and not Infantry, but with the added broken-down weight they failed to provide an improvement over the existing M2.
Goldsmith, Dolf. The Browning Machine Gun: Semper Fi FIFTY: Volume IV. Collector Grade Publications, 2008.