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The 6mm BR is a centerfire cartridge created for benchrest shooting. The cartridge is also known as the 6mm Bench Rest or simply 6 BR, and has also developed a following among varmint hunters because of its efficiency. There are two basic variants of very similar dimensions, known as the 6mm BR Remington and the 6mm Norma BR. ==Cartridge history== Soon after the introduction of the .308×1.5" Barnes cartridge, wildcatters and experimenters began developing their own wildcats based on the cartridge. By 1963 there were several .22 (5.7 mm) and .24 (6.1 mm) caliber cartridges based on the Barnes’ cartridge. The new cartridges’ accuracy and efficiency was noticed by the bench rest shooting community. The .24 caliber (6.1 mm) cartridge version became known as the 6mm Bench Rest or the 6mm BR due to its widespread use in the sport of bench rest shooting. Because the cartridge was a wildcat and was not standardized until several years later, several variations of the cartridge existed. Cases required fire forming in the chamber to provide the maximum in accuracy as chambers of the rifles varied from one to another. Several 6mm BR variants exist apart from the Remington and Norma versions: the 6mm BRX, 6mm Dasher, 6 mm BRBS 6 mm UBL. In 1978 Remington started manufacturing their Remington 40-X rifle in the 6mm BR and named their version of the cartridge the 6mm Bench Rest Remington. By 1988 Remington was also manufacturing ammunition. Remington continues to offer the 6mm BR Remington in the 40-X series rifles. The Remington version of this cartridge is now considered to be obsolete.〔 In 1996 Norma of Sweden introduced the 6mm Norma BR which was dimensionally similar to the 6mm BR Remington. However the chamber of the Norma version provided a longer throat making allowances for the seating of VLD bullets.〔 This is the most common variation of the cartridge used today. The 6mm Norma BR has become a popular chambering in match rifles used in ISSF and CISM and other 300 metres rifle disciplines.〔(Lapua Sport Shooting cartridges - the 6mm Norma BR )〕〔(6mm Norma BR DL match cartridge for 300 m rifle shooting product page )〕 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「6mm BR」の詳細全文を読む スポンサード リンク
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