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BB guns are a type of air gun designed to shoot spherical projectiles called BBs after the shot pellet of approximately the same size. Modern BB guns usually have a barrel with a bore and caliber of 0.177 inches (4.5 mm) and are available in many varieties. BB shot for modern BB guns is usually steel, plated either with zinc or copper to resist corrosion, and measure 0.171 to 0.173 inches (4.3 to 4.4 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.
The term is often incorrectly used to describe a pellet gun. Although in many cases, a BB can be fired in a pellet gun, pellets usually cannot be fired in a gun specifically designed for BBs. But many air gun models allow for both types of ammunition.
The term "BB" originated from the size of steel balls used in a shotgun shell of the same size. BB shot was normally 0.180 inches (4.6 mm), but tended to vary considerably in size due to the high allowable tolerances for shotgun shell use. Around 1900, Daisy, one of the earliest makers of BB guns, changed their BB gun bore diameter to 0.175 inches (4.4 mm), and began to market precision-made lead shot specifically for their BB guns. They called these simply "round shots", but the "BB" name was already well established, and everyone continued calling the guns "BB guns" and the shot "BB shot" or just "BBs".
Subsequently, the term "BB" became generic, referring to round shot of various calibers and materials. This included (and still includes) bearing balls, plastic round shot (such as used in airsoft), 0.177 caliber lead and steel shot, marbles and many others. It should also be noted that the ubiquitous usage of the term bearing for any steel ball is technically incorrect. A ball bearing is a mechanical bearing constructed with the intent of it being used to reduce friction or bear weight.
BB guns can use any of the operating mechanisms used for air guns. See the power source section of the air gun article. However, due to the inherent limited accuracy and short range of the BB, only the simpler and less expensive mechanisms are generally used for those guns designed to fire only BBs
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 (0.171 to 0.173 inches (4.3 to 4.4 mm)) than the internal diameter of the barrel (0.177 inches (4.5 mm)). 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.
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 275 ft/s (84 m/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 375 to 475 ft/s (114 to 145 m/s).
Multiple-pump pneumatic guns are also common. Many pneumatic pellet guns provide the ability to use BBs as a cheaper alternative to lead shot. Some of these guns have rifled barrels, but the slightly undersized BBs don't swage in the barrel, so the rifling does not impart a significant spin. These are the types of guns that will benefit most from using precision lead BB shot. The pneumatic BB gun can attain much higher velocities than the traditional spring piston types.
The last common type of power for BB guns is pre-compressed gas, most commonly the 12 gram CO2 powerlet. The powerlet, is a disposable metal flask containing 12 grams of compressed carbon dioxide, which expands to propel the BB. These are primarily used in pistol BB guns, and unlike spring-piston or pneumatic types, these are capable of rapid fire. A typical CO2 BB pistol uses a spring-loaded magazine to feed BBs, and a double action trigger mechanism to chamber a BB and cock the hammer. However some guns (either to stay true to the original gun or to make the trigger pull easier) do have a single action trigger. Either type of gun may also have blowback action, where CO2 will push the slide back in addition to firing a BB. When firing, the hammer strikes a valve hooked to the CO2 source, which releases a measured amount of CO2 gas to fire the BB. Velocities of CO2 powered BB pistols are moderate, and drop off as the pressure in the CO2 source drops. Many CO2 BB guns are patterned after popular firearms, and can be used for training as well as recreation.
Some gas-powered BB guns use a larger source of gas, and provide machine gun-like fire. These types, most notably the Shooting Star Tommy Gun (originally known as the Feltman) are commonly found at carnivals. The MacGlashan BB Gun, was used to train antiaircraft gunners in the United States Army Air Corps and United States Navy during World War II. A popular commercial model was the Larc M-19, which used 1 pound (454 g) canisters of Freon-12 refrigerant. These types have very simple operating mechanisms, based on a venturi pump. The gas is released in a constant stream, and this is used to suck the BBs up into the barrel at rates as high as 3600 rounds per minute.
It is possible to shoot competitively with a BB gun. The National Rifle Association youth shooting program has classifications for smoothbore BB guns, open to ages 14 – 18, and these classes are popular with youth groups such as Boy Scouts of America and 4H.
Most BB-firing airguns guns can shoot faster than 200 ft/s (61 m/s). Some airguns have the ability to fire considerably faster, even beyond 550 ft/s (170 m/s). Although claims are often exaggerated, a few airguns can actually fire a standard 0.177 caliber lead pellet faster than 1,000 ft/s (300 m/s), but these are generally not BB-firing guns.
A BB with a velocity of 150 ft/s (46 m/s) has skin piercing capability, and a velocity reaching 200 ft/s (61 m/s) can fracture bone. The potential can exist for delivering a fatal injury; this potential increases with velocity, but also rapidly decreases with distance. The effective penetrating range of a BB gun with a muzzle velocity of 400 to 600 feet per second (120 to 180 m/s) is approximately 60 feet (18 m). A person wearing jeans at this distance would not sustain serious injury. However, even at this distance a BB still might penetrate bare skin, and even if not, could leave a severe and painful bruise. The maximum range of a BB gun in the 400 to 600 ft/s (120 to 180 m/s) range is 240 to 350 yards (220 to 320 m), provided the muzzle is elevated to the optimum angle.
Steel BBs are also notably prone to ricochet off hard surfaces such as brick, concrete or metal. Eye protection is essential when shooting BBs. More so than when shooting lead pellets, since a BB bouncing off a hard surface can retain a large portion of its initial energy (pellets usually flatten and absorb energy), and could easily cause serious eye damage.
The U.S. Army trained recruits in quick kill techniques using Daisy Model 99 BB guns to improve soldiers using their weapons in the Vietnam War from 1967-1973. The technique was developed for the Army by Bobby Lamar "Lucky" McDaniel and Mike Jennings. The sights were removed from the BB guns for this training.
BB guns are regulated in the same manner as air guns, and there are large differences in their regulation[clarification needed], depending on the jurisdiction.
One of the most famous BB guns is the Red Ryder BB Gun by Daisy Outdoor Products, modeled after the Winchester lever-action rifle. First introduced in 1938, it became an iconic American toy, and is still in production today. It was prominently featured in A Christmas Story, in which Ralphie Parker requests one for Christmas, but is repeatedly rebuffed with the warning "You'll shoot your eye out". The movie's fictional BB gun, described as the "Red Ryder carbine-action, two hundred shot Range Model air rifle with a compass in the stock and this thing which tells time", was not a real gun. The Red Ryder featured in the movie was specially made to match author Jean Shepherd's story (which may be artistic license, but was the configuration Shepherd claimed to remember). The guns and a stand-up advertisement featuring the Red Ryder character appeared in a Higbee's store window in the film, along with dolls, a train, and Radio Flyer wagons.