An air gun is any gun that uses compressed air or gas, rather than an explosive charge, to launch a projectile. That distinction is what separates air guns from conventional firearms both mechanically and legally. They range from simple backyard BB guns to precision rifles capable of hunting medium-sized game, and they’ve been around in various forms since the late 1700s.
How Air Guns Work
Every air gun relies on the same basic principle: pressurized air or gas pushes a projectile out of the barrel. The differences come down to how that pressure is generated, and this is what defines the main categories of air guns on the market today.
Spring-piston guns use a coiled spring that compresses when you cock the barrel or a lever. Pulling the trigger releases the spring, which drives a piston forward and compresses air behind the pellet, launching it out the barrel. These are the most common entry-level air guns because they need no external power source. One cock, one shot.
Pneumatic guns store air that you manually pump into a chamber before firing. Single-stroke models require one pump per shot and are popular for target shooting. Multi-stroke models let you pump several times to build higher pressure, giving you some control over power. Pre-charged pneumatic (PCP) rifles sit at the top of this category. They store compressed air at 3,000 to 4,500 PSI and deliver multiple powerful shots on a single fill. Shooters refill them using a hand pump, a carbon fiber tank, or a high-pressure compressor.
CO2-powered guns use small cartridges of carbon dioxide gas. When the trigger is pulled, the gas expands rapidly and pushes the projectile out. CO2 guns maintain fairly consistent velocity across multiple shots until the cartridge runs empty, making them a popular choice for casual shooting and action-style pistols.
Pellets, BBs, and Caliber Sizes
Air guns fire two main types of ammunition: BBs and pellets. BBs are small, round, steel balls. Their shape makes them poor in terms of accuracy and prone to ricocheting off hard surfaces. Pellets are more refined. Most are made in a “diabolo” shape with a rounded or pointed head and a flared, cone-shaped skirt that stabilizes them in flight, much like a shuttlecock. This design makes pellets significantly more accurate and safer to shoot in controlled environments.
The most common calibers are .177, .22, and .25. A .177 caliber air gun is the standard for casual target shooting, backyard plinking, and competitive events. The .22 is the most versatile option. At around 21 foot-pounds of energy, a .22 caliber air gun handles small game like rabbits and squirrels effectively out to about 35 yards. Larger calibers like .25 and .30 are used for enthusiast benchrest shooting and hunting bigger animals such as raccoons and woodchucks, where higher energy (upward of 56 foot-pounds) allows clean kills at longer distances.
Speed and Power
Muzzle velocity in air guns typically ranges from about 600 feet per second on the low end to over 1,000 feet per second in high-powered models. A powerful .22 caliber PCP rifle, for example, can push a standard pellet at roughly 900 feet per second. Entry-level spring-piston rifles advertised at 1,000 feet per second often achieve that number only with the lightest pellets available. Switch to a normal-weight pellet and you’ll see velocities closer to 875 to 900 feet per second.
Heavier pellets fly slower but retain energy better at distance. The practical effect: a pellet fired at 800 feet per second and zeroed at 30 yards drops about 3.2 inches at 50 yards, while the same pellet at 600 feet per second drops roughly 6.6 inches at that distance. This is why choosing the right pellet weight matters just as much as the gun’s raw power rating.
Legal Status in the U.S. and U.K.
Under U.S. federal law, air guns are not classified as firearms. The Gun Control Act defines a firearm as any weapon that expels a projectile “by the action of an explosive.” Since air guns use compressed air or gas instead, they fall outside that definition entirely. The Bureau of Alcohol, Tobacco, Firearms and Explosives has applied this same reasoning to paintball guns and other pneumatic devices. That said, state and local laws vary widely. Some states set minimum age requirements, restrict where air guns can be discharged, or regulate them similarly to firearms in urban areas. Always check your local regulations.
In the United Kingdom, the rules are different. Air rifles producing up to 12 foot-pounds of muzzle energy can be owned without a firearms certificate (though age restrictions still apply). Anything above that threshold requires a certificate issued by local police, putting high-powered air rifles in the same regulatory category as conventional firearms.
Common Uses
Target shooting and plinking are the most popular uses for air guns worldwide. The low cost of pellets, minimal noise, and the ability to shoot safely in a backyard with a proper backstop make them accessible in ways that conventional firearms are not. Competitive air gun shooting is an Olympic sport, with events in both pistol and rifle categories using .177 caliber guns at 10-meter distances.
Pest control is another major application. Farmers and property owners use .177 and .22 caliber air guns to manage rats, squirrels, pigeons, and other pests without the noise, expense, or overpenetration risk of a conventional firearm. Hunting with higher-powered air guns has grown steadily, with PCP rifles in larger calibers now capable of taking game that would have required a powder-burning rifle a generation ago.
Air guns also serve as training tools. Their lower recoil and reduced noise make them ideal for teaching marksmanship fundamentals, and many competitive shooters use air rifles to practice trigger control and breathing techniques year-round.
A Surprisingly Long History
Air guns are not a modern invention. The Girardoni air rifle, invented in 1779, was the first repeating rifle to see regular military service. It used a tubular magazine and stored enough compressed air to fire multiple shots without reloading. The Habsburg military deployed it in the Austro-Turkish War of 1788 to 1791, eventually assigning the rifles to specialized sniper units. Because the gun produced no smoke when fired, the French considered it a terror weapon. Napoleon reportedly ordered the execution of any Austrian soldier captured carrying one.
Basic Safety Principles
Air guns deserve the same respect as any gun. The core rules are straightforward: always keep the muzzle pointed in a safe direction, even when you believe the gun is unloaded. Know your target and what lies beyond it. Steel BBs ricochet unpredictably off hard surfaces, so a proper backstop is essential. Pellet traps designed for air guns work well for indoor and backyard ranges. Never shoot at water, rocks, or other hard objects that can deflect a projectile in an unexpected direction.