<P> Subsequently, the term BB became generic, referring to any small spherical projectiles of various calibers and materials . This includes bearing balls often utilized by anti-personnel mines, . 177 caliber lead / steel shots used by air guns, plastic round balls (such as the pellets used by airsoft guns), small marbles and many others . It has become ubiquitous to refer to any steel ball, such as a BB, as a ball bearing . However, BBs should not be confused with a ball bearing, which is a mechanical component using bearing balls . </P> <P> BB guns can use any of the operating mechanisms used for air guns . However, due to the inherent limited accuracy and short range of the BB, only the simpler and less expensive mechanisms are generally used for guns designed to fire only BBs . </P> <P> Because the strength of the steel BB does not allow it to be swaged with the low energies used to accelerate it through the barrel, BBs are slightly smaller (4.3 to 4.4 mm (0.171 to 0.173 in)) than the internal diameter of the barrel (4.5 mm (0.177 in)). This limits accuracy because little spin is imparted on the BB . It also limits range, because some of the compressed air used to accelerate it is lost around the BB . Since a BB will easily roll unhindered down the barrel, it is common to find guns that use a magnet in the loading mechanism to hold the BB at the rear of the barrel until it is fired . </P> <P> The traditional, and still most common powerplant for BB guns is the spring piston, usually patterned after a lever - action rifle or a pump - action shotgun . The lever - action rifle was the first type of BB gun, and still dominates the inexpensive youth BB gun market . The Daisy Model 25, modeled after a pump - action shotgun with a trombone pump - action mechanism, dominated the low - price, higher - performance market for over 50 years . Lever - action models generally have very low velocities, around 84 m / s (275 ft / s), a result of the weak springs used to keep cocking efforts low for use by youths . The Daisy Model 25 typically achieved the highest velocities of its day, ranging from 114 to 145 m / s (375 to 475 ft / s). </P>

Where did the name bb gun come from