Cartridge Dimensions
The 7.62mm UKM has a 5.84 ml (90 grains) H2O cartridge case capacity. The exterior shape of the Lapua Magnum case was designed to promote reliable case feeding and extraction in bolt action rifles and machineguns alike, under extreme conditions.
7.62mm UKM maximum C.I.P. cartridge dimensions. All sizes in millimeters (mm).
Americans would define the shoulder angle at alpha/2 ≈ 20 degrees. The common rifling twist rate for this cartridge is 254 mm (1 in 10 in), 6 grooves, Ø lands = 7.62 mm, Ø grooves = 7.82 mm, land width = 2.79 mm and the primer type is large rifle magnum.
According to the official C.I.P. guidelines the 7.62mm UKM case can handle up to 470 MPa (68,167 psi) 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 for rifles very high maximum allowed chamber pressure level indicates that the cases of the .300 and .338 Lapua Magnum and 7.62mm UKM are built extremely sturdy to cope with this for rifles very high operating pressure. The large boltface combined with the high 470 MPa maximum pressure makes that the 7.62mm UKM should only be chambered in rifles that are capable of handling such large and fierce cartridges and thus high bolt thrust safely. Chambering such powerful super magnum cartridges in rifles intended for normal magnum rifle cartridges and using 470 MPa loads can cause serious or fatal injury to the shooter and bystanders.
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