7x57mm Mauser

The 7x57mm Mauser cartridge, also known as the 7x57mm, 7 mm Mauser, 7 mm Spanish Mauser and .275 Rigby, was developed by Mauser as a military cartridge in 1893, initially for use by the military forces of Spain. It was subsequently adopted by several other countries as the standard military cartridge. It is recognised as a milestone in modern cartridge design, and although now obsolete as a military cartridge, it remains in widespread international use as a sporting round. The 7x57mm has been deservedly described as "a ballistician's delight". Many sporting rifles in this calibre were made by British riflemakers, among whom John Rigby was prominent; and, catering for the British preference for calibres to be designated in inches, Rigby's called this chambering the .275 Rigby, after the measurement of a 7mm rifle's bore across the lands.

History
The Spanish military adopted a new Mauser rifle design in 1893. This took a smokeless powder centerfire cartridge with a bullet with a nominal diameter of 7 mm (0.285 in), and a case length of 57 mm - hence "7x57mm Mauser". It featured an 11 g (175 grain ) bullet with a muzzle velocity of about 700 m/s (2 300+ feet per second ). For the late 19th century, these ballistics were impressive. The change in bullet style, from a rounded tip to a pointed tip, was partially responsible for the cartridge's performance as it significantly reduced wind resistance within normal combat ranges.

Military round
The qualities of the 7x57mm Mauser as a military round were shown in the Spanish-American War and the Second Boer War in South Africa. Teddy Roosevelt and the Rough Riders took very heavy casualties attacking an inferior force armed with 7 mm Model 93 Mauser rifles. Likewise, British soldiers fighting in South Africa were obliged to re-evaluate rifle and ammunition design and tactics after facing Boer sharpshooters and snipers firing 7x57mm rounds with withering effectiveness, easily outranging the .303 British cartridge as regards accurate long-range fire. The .303 cartridge at that time was still using fine-grain black powder propellant, in contrast to the Mauser's higher-performance smokeless powder. The British kept the .303 cartridge, switched to a smokeless propellant (cordite), and updated their rifle to the Lee Enfield No. 1 Mk III.

Cartridge dimensions
The 7x57mm 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.



7x57mm 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, diameter of grooves = 7.24 mm, land width = 3.90 mm and the primer type is large rifle.

According to the official C.I.P. guidelines the 7x57mm case can handle up to 390 MPa (56564 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.

Sporting round
The ballistics of the 7x57mm Mauser quickly became very popular with deer and plains game hunters. The flat trajectory, along with the penetrating effects of the 7 mm bullet's high sectional density, ensured its place as a sportsman's cartridge. It was extremely popular in Africa, where it was used on everything up to and including elephants, for which it was particularly favored by legendary ivory hunter W. D. M. Bell, who shot 1,011 elephants with the diminutive 7x57mm, when most ivory hunters were using massive large caliber rifles. It was also the favored rifle of Eleanor O'Connor, wife of famous hunter and author Jack O'Connor. Eleanor accompanied her husband on multiple hunting expeditions all over the world, consistently taking game both large and small with the 7x57mm, a tribute both to the round's dependability and versatility, as well as her outstanding marksmanship. Though not quite so popular today, the 7x57mm is still produced by most major ammunition manufacturers and many modern rifles are available chambered for the cartridge, from custom and mass-market riflemakers in Europe and the USA.

Due to the age and metallurgical characteristics of the rifles for which it was originally designed, many of which are still functioning, most American commercially-manufactured rounds do not exploit the full potential of the cartridge, and opt for lower pressures. Some European-produced rounds are loaded to give higher velocities and pressures, and these can only be safely used in modern rifles chambered for the 7x57mm Mauser cartridge. This is not to say that older rifles, especially the stronger-built military rifles, cannot fire full power loads, but that commercial ammo companies are not willing to take the risk of lawsuits due to catastrophic failures. All firearms should be checked by a competent gunsmith and declared safe before any attempt is made to fire them.

The 7.92x57mm Mauser ("8 mm Mauser") and 7x57mm ("7 mm Mauser") cartridges are by no means the same cartridge, and they cannot be exchanged. Attempts to interchange the two cartridges could (and probably will) result in damage to property, injury and death.

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Cartridge:rifles