High Quality Content by WIKIPEDIA articles! BB guns are a type of air gun designed to shoot projectiles named BBs after the birdshot pellet of approximately the same size. These projectiles are usually spherical but can also be pointed/or triangular; those are usually used for bird hunting. Modern day BB guns usually have a barrel, with a bore and caliber of 0.177 inches (4.5 mm). BB shot for modern BB guns are usually steel, plated either with zinc or copper to resist corrosion, and measure 0.171 to 0.173 inches (4.34 mm to 4.39 mm) in diameter. Some manufacturers also still make lead balls of slightly larger diameter and which are generally intended for use in rifled BB gun barrels, as were formerly used in BB guns.