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| A shotgun "Did you know" | |
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| Tweet Topic Started: 16th November 2006 - 06:49 PM (110 Views) | |
| photopro | 16th November 2006 - 06:49 PM Post #1 |
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Facts and Figures Shotgun Calibres The bore number of a shotgun (e.g. 12-bore) is derived from the reciprocal weight in pounds of a spherical ball of lead which has a diameter equivalent to that of the gun barrel. Thus a 4-bore has the same internal diameter as a ¼-lb ball of lead and a 20-bore barrel will allow a ball of lead weighing 1/20-lb to pass along it. The calibres most commonly found in Britain are the four, eight and ten bores (used principally for wildfowling) and the more common twelve, sixteen, twenty and twentyeight bores. Bore Number & Diameter (inches): 8-bore .835 10-bore .775 12-bore .729 16-bore .662 20-bore .615 28-bore .550 Choke The question of choke is one that is often misunderstood. By the term choke, we mean the amount of constriction towards the muzzle end of a shotgun barrel which the gunmaker has incorporated to reduce the spread of pellets. Although other factors such as cartridge construction can also affect spread, the following table gives the theoretical effect of various degrees of choke; Choke Boring - Nominal Constriction (thou") - Diameter of Spread at 40 yards True cylinder (or skeet) - nil - 58 inches Improved cylinder - 5 51 - inches ¼-choke - 10 - 48 inches ½-choke - 20 - 45 inches ¾-choke - 30 - 42 inches Full choke - 40 - 40 inches Contrary to popular belief, the spread of pellets is not significantly affected by the calibre of the gun. The spread from a half-choke 12-bore will be the same as from a half-choke 20-bore. The only difference is that a lighter cartridge load will place fewer pellets in the pattern. British Shot Sizes Shot Size Nominal Diameter (inches) No. of Pellets per oz. AAA .20 35 BB .16 70 1 .14 100 3 .12 140 4 .11 170 5 .105 220 6 .10 270 7 .095 340 With thanks to British Fieldsports *good* photopro |
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7:52 PM Jul 11