bbgun

BB guns are air guns designed to shoot metallic ball projectiles called BBs (not to be confused with ball bearings), which are approximately the same size as BB size lead birdshot — 0.180 inches (4.6 mm) diameter. Modern BB guns usually have a barrel with a bore caliber of 4.5 mm (0.177 in), though many other varieties are available. These guns usually use steel BBs, either zinc- or copper-plated to resist corrosion, that measure 4.3 to 4.4 mm (0.171 to 0.173 in) in diameter and 0.33 to 0.35 g (5.1 to 5.4 gr) in weight. Some manufacturers still make the larger-diameter traditional lead balls that weigh around 0.48 to 0.50 g (7.4 to 7.7 gr), which are generally intended for use in rifled barrels (due to lead having better malleability).
The term "BB gun" is often incorrectly used to describe a pellet gun, which fires non-spherical projectiles. Although in many cases steel BBs can be fired from a pellet gun, the reverse situation is not true: pellets usually cannot be fired from a gun specifically designed for BBs. Similarly, the term is also often used incorrectly to describe airsoft guns, which shoot plastic balls that are larger but much less dense than metal BBs, and have significantly lower ballistic performance.

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