An air gun is a gun that uses compressed air or pressurized gas to fire projectiles instead of gunpowder. Where a traditional firearm relies on the combustion of a chemical propellant to generate force, an air gun stores or creates pressure mechanically, then releases it behind a pellet or BB to push it down the barrel. Air guns range from simple backyard plinking guns to precision competition rifles and powerful hunting platforms capable of taking game.
How Air Guns Generate Power
The part of an air gun responsible for propelling the projectile is called the powerplant. There are three main types, and each one creates pressure differently.
Spring-piston air guns use a mechanical spring and piston housed inside the gun. When you cock the barrel or a lever, it compresses a heavy spring. Pulling the trigger releases the spring, which drives the piston forward and compresses air behind the pellet. Everything needed to fire is built into the gun, so there are no cartridges to replace or tanks to refill. The tradeoff is noticeable recoil from the piston slamming forward and backward, plus physical effort from cocking the spring each time. This recoil can make consistent accuracy harder for beginners.
Pre-charged pneumatic (PCP) air guns store high-pressure air in an internal tank. You fill the tank beforehand using a hand pump, an electric compressor, or a larger external cylinder. Once filled, a PCP rifle can fire many shots at stable pressure before needing a refill. Because the air delivery is consistent and recoil is minimal, PCP guns are generally the most accurate type. Higher-end models include a regulator, a device fitted between the air tank and the firing valve that maintains a set pressure for each shot, further reducing variation.
CO2 air guns use small disposable cartridges of liquid carbon dioxide, typically inserted into the grip or stock. Once the cartridge is punctured, the gun is ready to fire with no pumping or cocking effort. The trigger pull is smooth and recoil is light, making CO2 guns popular for casual shooting and action-style pistols. The downside is that pressure drops as the cartridge empties and fluctuates with temperature, so performance can dip in cold weather or during long shooting sessions. Some newer high-end models use larger cylinders filled with compressed air or nitrogen, which offer higher operating pressures and better thermal stability.
Pellets, BBs, and Other Projectiles
Air guns fire two main types of ammunition: pellets and BBs. The distinction matters more than most beginners realize.
Pellets are typically made of lead and come in an aerodynamic “diabolo” shape, pinched in the middle with a flared skirt at the back. This design stabilizes the pellet in flight and makes it significantly more accurate than a BB over distance. Pellets also come in several tip shapes suited to different purposes. Wadcutter pellets have a flat tip ideal for punching clean holes in paper targets. Domed pellets retain energy well at range and are a good general-purpose choice. Hollow-point pellets expand on impact, making them a common pick for pest control and hunting.
BBs are small, round, and usually made of steel coated in copper or zinc. They come in one standard size (4.5mm / .177 caliber) and are inexpensive, which makes them appealing for high-volume plinking. But their spherical shape is less aerodynamic, so accuracy drops off faster at longer distances. Steel BBs can also ricochet more easily than lead pellets, which is worth keeping in mind when choosing a backstop.
Common Calibers and What They’re For
Air gun calibers range from .177 all the way up to .50, though three sizes cover the vast majority of shooters:
- .177 caliber: The most popular size worldwide. These lightweight pellets fly fast and flat, making them the standard for target shooting, competition, and backyard pest control. Olympic and competition air rifles and pistols are chambered in .177.
- .22 caliber: Heavier than .177, with a strong balance of accuracy and hitting power. This is the go-to for hunting small game like squirrels, rabbits, and birds.
- .25 caliber: Heavier still, delivering more energy on impact. Best suited for hunting with high-powered PCP rifles where knockdown power matters more than flat trajectory.
Larger calibers like .30, .357 (9mm), .45, and .50 exist for big-bore air rifles designed to hunt larger animals, but these are specialized tools that require powerful PCP platforms and significantly more investment.
Speed and Energy Ranges
Air gun performance is measured in two ways: muzzle velocity (how fast the projectile travels, in feet per second) and muzzle energy (how hard it hits, in foot-pounds of energy, or FPE).
Competition air rifles and pistols used in Olympic and national events fire in the 450 to 580 fps range. Manufacturers have found through testing that velocities in the 560 to 580 fps window produce optimum accuracy for precision shooting. On the other end of the spectrum, hunting-grade PCP rifles in larger calibers can push well past 900 fps and deliver 40 or more foot-pounds of energy at the muzzle.
For practical purposes, energy matters more than speed when you’re choosing an air gun for a specific task. Target shooting and backyard plinking require only 6 to 12 FPE. Small game hunting (squirrels, rabbits, birds) calls for at least 12 FPE, with most experienced hunters recommending the 12 to 20 FPE range in .22 or .25 caliber. Larger game requires 40 FPE or more, which puts you firmly in big-bore PCP territory.
What People Use Air Guns For
Target shooting is the single largest use. Air guns are used in Olympic competition, collegiate programs, Junior ROTC, and backyard informal shooting. The low noise, minimal recoil, and inexpensive ammunition make them ideal for developing marksmanship skills. Many competitive shooters start on air rifles before transitioning to firearms, and some never leave.
Pest control and small game hunting are the next most common applications. A .22 caliber air rifle producing 12 to 20 FPE is effective and relatively quiet, which makes it practical in suburban or semi-rural areas where a firearm would be unsafe or illegal to discharge. Hunters appreciate that air guns don’t produce the same noise disturbance, and the lower energy means less risk of a projectile traveling dangerously far beyond the target.
Recreational plinking, shooting tin cans and spinners in the backyard, accounts for a huge share of air gun sales. CO2 pistols that replicate the look and feel of popular handgun models are especially popular here, offering a low-cost way to practice handling and trigger control.
A Surprisingly Long History
Air guns are not a modern invention. One of the most remarkable examples is the Girardoni air rifle, designed by Austrian gunsmith Bartolomeo Girardoni around 1779. It was a repeating rifle with a 20-round tubular magazine, powered by a detachable air reservoir built into its club-shaped stock. At roughly 800 psi, a full reservoir could fire 30 shots at useful pressure, pushing lead balls at about 600 fps. The Austrian military issued approximately 1,300 of them, and each rifleman carried the rifle, three air reservoirs, and 100 lead balls.
The Girardoni’s most famous appearance was on the Lewis and Clark Expedition from 1803 to 1806. Meriwether Lewis carried one and fired it at least 16 times in demonstrations for Native American tribes they encountered along the route. Its ability to fire repeatedly without smoke or loud reports made a strong impression.
Safety Considerations
Air guns are not toys, even though they’re sometimes marketed alongside toy guns. A pellet traveling at 600 fps or more can cause serious injury or death, and even low-powered BB guns can damage eyes and break skin. Most states prohibit minors from possessing non-powder guns unless under direct adult supervision. Federal law requires that lookalike firearms (guns that could be mistaken for real firearms) carry a permanently affixed blaze orange barrel plug or be made from transparent materials, though actual air guns sold to adults may not always have these markings.
The same fundamental rules that apply to firearms apply to air guns: treat every gun as if it’s loaded, never point it at anything you don’t intend to shoot, keep your finger off the trigger until you’re ready to fire, and always know what’s behind your target. Steel BBs in particular demand a solid backstop, since they bounce off hard surfaces unpredictably.