- Both these rounds used by heavy machine-guns, .50 BMG and 12.7X108, have the same caliber and are not interchangeable. The Russian 12.7X108 round has a cartridge case 9mm longer than the US .50 BMG [12.7X99]. Each of these two 12.7mm rounds use a different type of propellant, the bullet shape is also different and the rimless cartridge case capacity isn’t the same. —> QUESTION: Is the Russian 12.7X108 round considered to be equivalent of the US .50 BMG [12.7X99] or is it more powerful??? Liviu 07/12/08
The performance of the two rounds is close enough to be considered effectively identical. The 12.7x108 has a bigger-capacity case but is normally loaded to a lower pressure (c.44,000 psi cf 55,000) which gives it slightly less performance.
Of more significance is the fact that more advanced projectiles have been available in the .50 (Multipurpose and APDS), but the 12.7mm is catching up in this respect.