7×57mm Mauser

The 7×57mm Mauser (designated as the 7 mm Mauser or 7×57mm by the SAAMI and 7 × 57 by the C.I.P.) is a first-generation smokeless powder rimless bottlenecked rifle cartridge. It was developed by Paul Mauser of the Mauser company in 1892 and adopted as a military cartridge by Spain in 1893. It was subsequently adopted by several other countries as the standard military cartridge, and although now obsolete as a military cartridge, it remains in widespread international use as a sporting round. The 7×57 Mauser (originally known in Britain as the .275) was a popular stalking cartridge and sporting rifles in this chambering were made by the famous British riflemakers, such as John Rigby, Holland and Holland, Westley Richards and others. British cartridge nomenclature designated caliber in inches, and the cartridge was known as the .275 bore after the measurement of a 7 mm rifle's bore across the lands. The cartridge is today often erroneously referred to as the ".275 Rigby", however neither Rigby & Sons nor Kynoch (the major UK ammunition manufacturer of the period) sold the cartridge in boxes labeled .275 Rigby - instead it was always marked ".275 bore" (Rigby) or 7mm Mauser (Kynoch) and it is doubtful the cartridge was ever referred to as the ".275 Rigby" during its golden period.

Paul Mauser visited the Kingdom of Spain in 1892 after the delivery of trial rifles in 1891 and brought with him a new rifle designed to use a new cartridge of 7 mm caliber. Judging by the dimensions of the casing, it was developed from Mauser's Patrone 88 adopted into German service: in fact, its derivative, 6.5×57mm Mauser, was marketed as M88/57/6.5 mit und ohne Rand in a 1921 catalog. Like the 7.65×53mm Mauser introduced in 1889, he had developed the 7×57mm Mauser cartridge for use with the new smokeless propellant, introduced as Poudre B in the 1886 pattern 8×50mmR Lebel, which started a military rifle ammunition revolution. At the time of its development 7×57mm Mauser was a high-performance smokeless-powder cartridge.

The Mauser Model 1892 rifle turned out to be a transitional design that was manufactured in limited numbers for the Spanish Army. It was quickly improved to the Mauser Model 1893 featuring a new internal box magazine where the cartridges were stored in a staggered column. The Spaniards were so impressed with the Mauser Model 1892 and 1893 rifles and their new 7×57mm Mauser cartridge that they not only ordered rifles and ammunition from Mauser, but also awarded him the Grand Cross of the Spanish Military Order of Merit, the highest decoration Mauser ever received.

The 7×57mm cartridge has 3.90 ml (60 grains H₂O) cartridge case capacity. The exterior shape of the case was designed to promote reliable case feeding and extraction in bolt-action rifles and machine guns alike, under extreme conditions.

7×57mm maximum C.I.P. cartridge dimensions. All sizes in millimeters (mm).

Americans would define the shoulder angle at alpha/2 ≈ 20.55 degrees. The common rifling twist rate for this cartridge is 220 mm (1 in 8.66 in), 4 grooves, diameter of lands = 6.98 mm (0.275 in), diameter of grooves = 7.24 mm (0.285 in), land width = 3.90 mm (0.154 in) and the primer type is large rifle.

European 7 mm cartridges all have 7.24 mm (0.285 in) grooves diameter. American 7 mm cartridges have 7.21 mm (0.284 in) grooves diameter.

According to the official C.I.P. (Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives) rulings the 7×57mm case can handle up to 390.00 MPa (56,565 psi) P_max 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.