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The .220 Swift (5.56×56mmSR) is a semi-rimmed rifle cartridge developed by Winchester and introduced in 1935. It was the first factory loaded rifle cartridge with a muzzle velocity of over .〔Speer Reloading Manual Number 10 1979〕 Until the introduction of the .223 WSSM the .220 Swift was the fastest commercial cartridge in the world. The Swift is a large cased .224 caliber cartridge and bullet that was created for small game such as prairie dogs, groundhogs and other vermin (or "varmints" in the US) such as marmots. Upon its introduction it astounded the varmint hunting world by being fully faster than its nearest competitor, which was the .22 Hornet (also .224 caliber). It was found to be an extremely accurate cartridge as well.〔〔(220 Swift article ) at Gunners Den〕 Due to its very high velocity its bullet drop allows dead on sighting on game such as groundhogs to ranges out to , and it is still considered an excellent cartridge for taking varmints by experienced Swift shooters.〔 The original factory load from Winchester provided a bullet launched at 4,100 feet per second (1,250 m/s). Handloaders could marginally improve on this but only at maximum loads. The Swift can be loaded with light bullets to reach .〔Cartridges of the World 12th Edition ISBN 978-0-89689-936-0〕 In recent times .224" bullets have been developed for use in high velocity .22 caliber rifles for taking larger game and long-distance shooting. Heavier bullets perform best in rifles that have an appropriate rifling twist rate taking into consideration the diameter, length, and other physical properties of the projectile. ==History== The prototype for the .220 Swift was developed in 1934–35 by Grosvenor Wotkyns who necked down the .250-3000 Savage as a means of achieving very high velocities. However the final commercial version developed by Winchester is based on the 6mm Lee Navy cartridge necked down. The .220 Swift was developed by Winchester and introduced in 1935 as a new caliber for their Model 54 bolt-action rifle. When the Winchester Model 70 bolt action was first issued in 1936, the .220 Swift was one of the standard calibers offered and continued to be until 1964 when it was discontinued.〔 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「.220 Swift」の詳細全文を読む スポンサード リンク
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