12 gauge, shotgun, chest full of carbon (boom-boom)
The caliber of shotguns is measured in terms of gauge or bore. 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 and 9 mm (.355 in.) and .22 (5.5 mm) rimfire calibres have also been produced.
Chest full of carbon= Carbon is a chemical element. It is one of the many elements used to make bullets. A chest full of carbon would signify a chest full of bullets.
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