When someone says airgun these days they probably mean a spring-piston airgun. Spring-piston airguns are the easiest airguns to shoot, maintain and own. The spring-piston gun most shooters start with is the break barrel. The break barrel airgun is cocked by holding the stock in one hand and breaking the airgun in half at the breech holding the barrel with the other. This action of breaking the airguns moves a piston backward within the receiver as well as compressing a stout spring behind it. The trigger sear clicks into a notch in the piston and holds the whole works in tension. With a break barrel airgun the pellet is placed directly into the breech and the barrel is tipped back into position making it ready to fire. Take the safety off and put positive pressure on the trigger. When the sear released the piston, it moves forward briskly with the power of a big spring behind it. All this action pushes a column of air forward into the rear end of the pellet sitting in the breech. The effect of all this causes the pellet to move briskly out the barrel towards the target of you choice. Spring-piston airguns are cocked by breaking the barrel, cocking an underlever, a side lever, or a top lever. Spring-piston airguns are very reliable and long lived. The worst thing you could do to any spring-piston airguns is to “dry fire” it, that is, fire it without a pellet in the breech. If that happens the piston head is smashed into the front of the receiver because the missing pellet cannot offer the needed resistance to the air column. This resistance cushions the piston from the tremendous energy the compressed spring releases to move the air column. Spring-piston airguns last a long time, but the springs do wear out after a while. A spring piston replacement and piston seal change are relatively cheap and very easy for an airgun smith to accomplish. Most firearms shooter like the recoil sensation felt when shooting a spring airgun. This is a smooth steady push to the shoulder as the spring inside the airgun does its work pushing the pellet out the barrel.
CO2 Air Guns
As their name implies, these airguns are powered by CO2. It is used in some of the cheapest non- precision airguns along with the highest of the high-tech 10 meter match airguns. Kept at room temperature, CO2 is approximately 900-1000 psi and very consistent, but raise or lower the temperature and the point of impact of a CO2 airgun will change. The real issue with CO2 as a power plant is for the airgun hunter or plinker. The airgun hunter who sights in on a warm day and goes out to hunt on a cool one or visa-versa will not know where the airgun will hit. A temperature change during the day will also be a problem. CO2 airguns are generally easy to cock and recoilless to shoot. The match CO2 airguns are very consistent and incredibly accurate at 10 meters.