7.62 x 53R

Round length: 77.00 mm (54R: 77.16)
Case length: 53.50 mm (54R: 53.72)
Rim diameter: 14.40 mm (54R: 14.48)
Bullet diameter: 7.85 mm (54R: 7.92)

From Wikipedia, the free encyclopedia

The 7.62 x 53R (aka 7.62 x 53R Finnish) rifle cartridge is a Finnish design based on the 7.62 x 54R Russian dating back to 1891.

After gaining its independence in 1917 and after the Finnish Civil War of 1918, large numbers of Model 1891 Mosin-Nagant rifles were in the hands of the Finnish military. As the old barrels were worn out, they were replaced by new .308" (7.83 mm) barrels and the leftover 7.62x54R cartridges being in short supply, a domestic product was needed. This gave birth to the 7.62x53R.

The 7.62 x 53R is practically interchangeable with the 7.62 x 54R, the 54R will fit into the smallest allowed chamber size for the 53R, but is nevertheless a different cartridge made to different CIP standards. Using military steel-jacketed 54R Russian ammunition in weapons made for 53R Finnish is not recommended, as it may rapidly wear out the barrel. Even worse, there is a possibility that the resulting pressure from the steel-jacketed larger diameter bullet is too much and firing it may result in severe damage to both the rifle and the shooter. Using the 53R Finnish in a rifle made for the 54R Russian is however safe, although it may result in accuracy well below the weapon's potential.

The cartridge remains in military use to this day, although it is now only used by the 7.62 TaK 85 sniper rifle. PKM machineguns and other Russian weapons in Finnish use are using the 7.62 x 54R exclusively.