What cartridge was developed in 1910 and is currently used in the M2 machine gun?
.50 BMG The .50 Browning Machine Gun (.50 BMG, 12.7×99mm NATO and designated as the 50 Browning by the C.I.P.) is a cartridge developed for the Browning .50 caliber machine gun in the late 1910s. Entering service officially in 1921, the round is based on a greatly scaled-up .30-06 cartridge. Under STANAG 4383, it is a standard cartridge for NATO forces as well as many non-NATO countries. The cartridge itself has been made in many variants: multiple generations of regular ball, tracer, armor-piercing (AP), incendiary, and saboted sub-caliber rounds. The rounds intended for machine guns are linked using metallic links.
8mm Roth–Steyr The 8mm Roth–Steyr is a military centerfire pistol cartridge adopted by the Austro-Hungarian cavalry in 1907 for the "Repetierpistole" M7—the first self-loading pistol adopted by a major military power. The cartridge headspaces on the mouth of the case. Ammunition was typically packaged in a unique ten-round charger. Austrian military production contained greased un-plated steel-jacketed bullets. A few private firms in Austria manufactured ammunition with cupro-nickel-jacketed bullets. Fiocchi Munizioni manufactured 8mm Roth–Steyr cartridges as one of its specialty lines as recently as 2017. An alternative source of reloadable cartridge cases is a labor-intensive process of base forming, trimming, neck reaming and resizing .30 Carbine brass.