7.62×53mmR

The 7.62×53mmR is a rimmed, bottlenecked rifle cartridge adopted by Finland in 1918, developed from the Russian 7.62×54mmR that the newly independent country inherited in Mosin–Nagant rifles left over from Imperial Russian service. It remains Finland’s standard rifle and machine-gun cartridge for the arms still in reserve or ceremonial use, chambered in the Finnish-built m/28, m/28-30 and m/39 Mosin–Nagant variants and the Lahti-Saloranta M/26 light machine gun.

This is a distinct cartridge from the 7.62×54mmR it descends from, not an alternate name for it. The two share a rim diameter and are near-interchangeable in the chamber, but Finnish production held its own dimensional standard, separately registered with C.I.P., with a case length of 53.5 mm against the Russian round’s 53.72 mm and its own maximum pressure of 390 MPa — tighter, domestically produced tolerances that Finnish shooters and collectors still distinguish from wartime and Soviet-era 54mmR ammunition.

This entry carries the full C.I.P. dimensional standard, verified against the published datasheet. One ball load’s bullet mass, converted from a published 185.4 grains, is recorded as estimated because the source Wikipedia table does not credit a factory sheet. No test barrel length is stated anywhere in the cited article, so no velocity is recorded and the cartridge computes no muzzle energy or trajectory; no ballistic coefficient is published for it free either.