12.7×108mm

The 12.7×108mm cartridge is a 12.7 mm heavy machine gun and anti-materiel rifle cartridge used by the former Soviet Union, the former Warsaw Pact, modern Russia, China and other countries. It was invented in 1934 to create a cartridge like the German 13.2mm TuF anti-tank rifle round and the American .50 Browning Machine Gun round.

It is used in the same roles as the NATO .50 BMG (12.7×99mm NATO) cartridge. The two differ in bullet shape and weight, and the casing of the 12.7×108mm is slightly longer, and its larger case capacity allow it to hold slightly more of a different type of powder. The 12.7×108mm can be used to engage a wide variety of targets on the battlefield, and will destroy unarmored vehicles, penetrate lightly armored vehicles and damage external ancillary equipment (i.e.: searchlights, radar, transmitters, vision blocks, engine compartment covers) on heavily armored vehicles such as tanks. It will also ignite gasoline and—since 2019—diesel fuel. Armor-piercing ammunition will penetrate around 25 mm of armor. Normal full metal jacket ammunition will only dimple tank armor, causing no damage.

Cartridge dimensions
The 12.7×108mm has 22.72 ml (350 grains) H2O cartridge case capacity.

Americans would define the shoulder angle at alpha/2 ≈ 18.16 degrees.

According to guidelines the 12.7×108mm case can handle up to 360 MPa (52,213 psi) piezo pressure. In C.I.P. regulated countries every rifle cartridge combo has to be proofed at 125% of this maximum CIP pressure to certify for sale to consumers.

Incorrect interchangeability claims
It is often claimed that the US .50 BMG (12.7×99mm NATO) cartridge can be fired in Soviet/Russian 12.7×108mm machine guns. The 12.7×108mm was even called a ".51 caliber". This often claimed interchangeability is an assumption made from the 12.7×108mm being listed as ".511 caliber" in US intelligence publications during the Vietnam War. The bullets used for both cartridges are ~.51 inches in diameter. .50 caliber, 1/2 of an inch, is the diameter of the hole bored down the barrel of the gun first. Then rifling is cut all around the bored hole to a depth of .005". Thus, .500 + .005 + .005 = .510." Upon firing, the bullet engages the rifling, and .005" grooves are pressed into the surface of the bullet to impart spin to stabilize the bullet. Despite the similar bullet diameters, the dimensional differences between the two cartridges prevent either being correctly chambered in a firearm designed for the other.

Aerial weapons using ammunition

 * ShVAK cannon (12.7 mm version)
 * Berezin UB
 * Yu-12.7