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The .303 British (designated as the 303 British by the C.I.P.〔(C.I.P. TDCC datasheet 303 British )〕 and SAAMI〔(SAAMI Drawing 303 British )〕) or 7.7×56mmR, is a calibre (with the bore diameter measured between the lands as is common practice in Europe) rimmed rifle cartridge first developed in Britain as a black-powder round put into service in December 1888 for the Lee–Metford rifle. In 1891 the cartridge was adapted to use smokeless powder.〔 It was the standard British and Commonwealth military cartridge from 1889 until the 1950s when it was replaced by the 7.62×51mm NATO.〔 ==Cartridge dimensions== The .303 British has 3.64 ml (56 grains H2O) cartridge case capacity. The pronounced tapering exterior shape of the case was designed to promote reliable case feeding and extraction in bolt action rifles and machine guns alike, under challenging conditions. 400px .303 British maximum C.I.P. cartridge dimensions. All sizes in millimeters (mm). Americans would define the shoulder angle at alpha/2 ≈ 17 degrees. The common rifling twist rate for this cartridge is 254 mm (1 in 10 in), 5 grooves, Ø lands = , Ø grooves = , land width = and the primer type is Berdan or Boxer (in large rifle size). According to the official C.I.P. (Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives) rulings the .303 British can handle up to Pmax 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 means that .303 British chambered arms in C.I.P. regulated countries are currently (2014) proof tested at PE piezo pressure. The SAAMI (Sporting Arms and Ammunition Manufacturers' Institute) Maximum Average Pressure (MAP) for this cartridge is piezo pressure (45,000 CUP).〔(ANSI/SAAMI Velocity & Pressure Data: Centerfire Rifle )〕 The measurement is the nominal size of the bore measured between the lands which follows the older black powder nomenclature. Measured between the grooves, the nominal size of the bore is . Bores for many .303 military surplus rifles are often found ranging from around up to . Recommended bullet diameter for standard .303 British cartridges is .〔Hornady Handbook of Cartridge Reloading, Rifle-Pistol, Third Edition, Hornady Manufacturing Company, 1980, 1985, p.253-254.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「.303 British」の詳細全文を読む スポンサード リンク
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