8mm x 54mmR - 8mm x 55mm Chinese - 7.92mm x 55mmThe cartridge is primarily used with two barrels types, a standard 8mm barrel with a 5 groove right-hand 1 in 240mm (1 in 9.45 in) barrel twist, and an accurized barrel with a slightly different barrel twist and 3 grooves. The accurized barrel utilizes as a polygonal rifling twist, is hammer forged and nitrided, which has a shorter life and worse corrosion resistance, but is more accurate. Due to the polygonal rifling, the barrels life is actually slightly longer than the standard rifle barrel, despite the nitriding process. It also is designed to be stiffer and heavier, is free-floating (lacking an aluminum heat sink), and has a muzzle break which contours to the rifle's barrel grooves and increases barrel harmonic stabilization, like with the
FR F1 rifle. The standard barrel uses an aluminum heatsink in the handguard to help dissipate heat and is chrome plated for corrosion resistance, but is consequently less accurate, particularly given that it normally uses standard 10 gram AP ammunition instead of match grade ammunition. Either gun can use either ammunition, however the accurized barrel has a shorter range with the 10 gram AP than the standard battle rifle cartridge, having a slightly different barrel twist. Both barrels come in 20 inch and 14.5 inch barrel configurations for full length and carbine-length weapons, however the sniper variant is rarely used with the 14.5 inch barrel. The velocity produced by these barrels is 850 m/s and 785 m/s respectively for the 10 gram AP cartridge, and 790 m/s and 735 m/s for the 12.8 gram sniper cartridge, or 3600 and 3080 joules from each barrel length, and 4000 joules and 3450 joules from each barrel length from the sniper rounds. The Sniper cartridge is slightly more powerful, with 4000 joules vs. 3600 for the standard cartridge, giving it slightly more recoil as well, making it harder to use in rapid fire. The 10 gram armor piercing round has a G1 BC of .408 (referred to as the
D11) and remains super sonic until 1000 yards, and has the same energy than a 5.56mm x 45mm NATO at 400 yards (1800 joules), and the same energy as the .357 magnum at 700 yards (1000 joules), with as much energy as a handgun round at it's supersonic range of 1000 yards (500 joules). The 12.8 gram
sniper round has a G1 BC of .595 (referred to as the
D23) and remains super sonic until 1325 yards, and has the same energy than a 5.56mm x 45mm NATO at 650 yards (1800 joules), and the same energy as the .357 magnum at 1075 yards (1000 joules), with as much energy as a handgun round at 1900 yards (500 joules).
The 8mm was chosen by the Chinese to be a slightly more aerodynamic, more powerful cartridge over the 7.62mm x 51mm NATO and 7.62mm x 54mmR cartridges. It is slightly lighter weight than the 7.62mm x 51mm NATO, but is also more aerodynamic and more powerful, giving it better characteristics. Given the lower quality of the bullet composition and casing material (which is usually steel), the 8mm performs better, and is similiar enough to captured ammunition by the Chinese used in WWII and consequently other engagements. As the chinese have been supplied with a large number of german weapons, their experiments with german cartridges were not uncommon, and lead to the development of the 8mm Chinese. Some consider the round to simply be a rejection of Russian and American cartridges, which is partially true as the same performance can be replicated from these cartridges if using better bullets, and the high aerodynamics are not unique to the 8mm round. The rounds also are heavy enough to still provide good armor penetration and stopping power, which provides the ballistics desired by the chinese.
