The 7.62×45mm (designated as the 7,62 × 45 by the C.I.P.) is a rimless bottlenecked intermediate rifle cartridge developed in Czechoslovakia. It is fired by the Czech Vz. 52 rifle, Vz. 52 light machine gun, and ZB-53 machine gun. The round was later dropped from use when the Czech converted to the standard Warsaw Pact round, the 7.62×39mm (fired by vz. 52/57 rifle and vz. 52/57 light machine gun). Its muzzle velocity and muzzle energy are slightly higher than that of the 7.62×39mm cartridge. Cartridge dimensions The 7.62×45mm has 2.79 ml (43.1 grains H2O) cartridge case capacity. The exterior shape of the case was designed to promote reliable case feeding and extraction in bolt action and semi-automatic rifles and machine guns alike, under extreme conditions. 7.62×45mm maximum C.I.P. cartridge dimensions. All sizes in millimeters (mm). Americans would define the shoulder angle at alpha/2 ≈ 24.9 degrees. The common rifling twist rate for this cartridge is 280 mm (1 in 11.03 in), 4 grooves, Ø lands = , Ø grooves = , land width = and the primer type is Berdan or Boxer (in large rifle size). According to the official C.I.P. (Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives) rulings the 7.62×45mm can handle up to Pmax piezo pressure. In C.I.P. regulated countries every rifle cartridge combo has to be proofed at 125% of this maximum C.I.P. pressure to certify for sale to consumers. This means that 7.62×45mm chambered arms in C.I.P. regulated countries are currently (2014) proof tested at PE piezo pressure. Non-official dimensions There are definite differences in reported dimensions from non-official sources for this cartridge. Some of this may be accounted for by small errors in conversion from metric to inches, while others such as loaded length may additionally be attributed to different lengths of bullets being measured in loaded rounds. A sample list of various measurements is in the table below. Dimensionally similar The 6.5mm Grendel cartridge is extremely close dimensionally. It is a common option used when re-barreling the Czech Vz.52 carbine to an easily available factory or Boxer primed reloadable cartridge. 6.5 Grendel was originally designed for the AR15 class of firearms, and therefore has power level (pressure) ratings that are within the limits of that class. As such, the C.I.P. listed pressure levels for the 6.5 Grendel are lower than those listed by the C.I.P for the 7.62x45. Wildcats The 7.62×45mm