Before the Browning M2, there was a series of Colt commercial .50 caliber machine guns. The .50 BMG (12.7x99mm) cartridge began development in 1918, and after the end of the war Colt and John Browning finalized a water-cooled machine gun to use it. While military experimentation and development continued, Colt introduced the gun as the Model 1924, and sold it in both water-cooled and air-cooled varieties. The names were changed in 1932/3 to become the MG52 (water cooled) and MG53 (air cooled) to keep the guns sounding modern. In addition, they introduced the MG52-A, which was a water cooled model with interchangeable feed to accommodate vehicle and dual mounts.
The Model 1924/MG52 has a number of early features that would be changed when the M2 become the standard model. These have simple straight-line charging handles, instead of the camel system of the M2. They have rear sights like the early M1917 .30 caliber guns, manual safeties, and are built on dedicated water-cooled receivers (the M2 would introduce a universal receiver). Only a few thousand of these were made by World War Two, and their production did not resume after the war.