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A spotting rifle is a small-calibre rifle used as a sighting device for artillery. The ballistics of the spotting rifle are matched to those of the artillery piece,〔 so that if a shot from the spotting rifle lands on the target, it may be assumed that the main weapon will also do so. == Anti-tank recoilless rifles == Spotting rifles were most commonly used with recoilless rifles as anti-tank artillery, from the 1950s to the 1970s. These weapons are used for direct fire with line-of-sight visibility to the target. As recoilless rifles have a relatively low muzzle velocity and thus a high trajectory, accurate ranging is important〔Wombat, User Handbook, p. 2〕 An optical sight can measure the bearing to a target, but not easily or accurately measure the range. Optical rangefinders were too large for lightweight portable artillery, and the later development of laser rangefinders would in turn make spotting rifles obsolete. The British BAT series of 120 mm anti-tank recoilless rifles used a variety of sighting systems. The original BAT used a purely optical sight. The MoBAT, a lightweight and more portable version, had a 7.62mm calibre Bren light machine gun.〔Jane's Weapon Systems, 1977, MoBAT, p. 391〕 The final version, the WOMBAT, used the same American Remington M8C .50 in〔Wombat, User Handbook, Section 5. Spotting Rifle 0.5in M8C pp. 25—33〕〔Jane's Weapon Systems, 1977, L6 Wombat, p. 391〕 as the M40 recoilless rifle. Both of these were used as gas-operated semi-automatic rifles. The .50 was not, as often assumed, a development of the .50 M2 machine gun using the 12.7mm×99mm NATO cartridge, but was a shortened 12.7mm×76mm cartridge. Where a vehicle, such as the M50 Ontos, used multiple barrels, spotting rifles were usually provided for each barrel so that each could be accurately boresighted to its own barrel. The Ontos used six barrels with four spotting rifles; two without, to avoid making an already tall vehicle even higher. This provision may have been over-generous, although it did also increase the magazine capacity available for repeated ranging shots. Many photographs of the Ontos in service in Vietnam show it with only two of the spotting rifles installed in their mounts.〔:File:M50-ontos-vietnam.gif〕 The Ontos also often only carried four or even two main rifle tubes. 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「Spotting rifle」の詳細全文を読む スポンサード リンク
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