The caliber of shotguns is measured in terms of gauge (U.S.) or bore (U.K.). The gauge number is determined by the weight, in fractions of a pound, of a solid sphere of lead with a diameter equal to the inside diameter of the barrel. So, a 10 gauge shotgun nominally should have an inside diameter equal to that of a sphere made from one-tenth of a pound of lead. By far the most common gauges are 12 (0.729 in, 18.5 mm diameter) and 20 (0.614 in, 15.6 mm), although .410 (= 67), 32, 28, 24, 16, and 10 (19.7 mm) gauge also exist. Ammunition manufacturer CCI produces 9 mm (.355 in.) and several other popular pistol calibers up to .45 ACP as well as .22 (5.5 mm) for firing from handguns. These are commonly called snake shot cartridges. rimfire caliber. Larger gauges, too powerful to shoulder, have been built, but were generally affixed to small boats and referred to as punt guns. These were used for commercial waterfowl hunting, to kill large numbers of birds resting on the water. Although relatively rare, single and double derringers have also been produced that are capable of firing either .45 (Long) Colt or .410 shotgun shells from the same chamber; they are commonly known as "snake guns", and are popular among some outdoorsmen in the South and Southwest regions of the United States. There are also some revolvers, such as the Taurus Judge, that are capable of shooting the .45LC/.410 rounds; but as with derringers, these are handguns that shoot .410 shotgun shells, and are not necessarily considered shotguns.