The Three Basic Types of Airguns

by Ben Saltzman
Reprinted from the Beeman Precision Airgun Guide

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Airguns come in many shapes and forms. You know this to be true because you just might want to own one of these swell airguns but can't understand why Beeman imports so many when you want just one. I'll give you some basic information so that you can make a considered choice. Besides the question of caliber, modern airguns fit into three basic groups defined by their power plants (means of pushing a pellet out the barrel). 1. Pneumatic Airguns 2. Spring-Piston Airguns 3. CO2 Airguns.

Pneumatic Airguns

Pneumatic airguns use compressed air for power. The way you get the air compressed in the airgun depends on the type of pneumatic it is. The most common pneumatic airgun is the Multi-Stroke or sometimes called Pump-up type pneumatic airgun. To get the tiny bit of air compressed in a multi-stroke pneumatic takes, as the name implies, between two and ten strokes of the forend pump lever to get the internal pressure needed to power the pellet out the barrel at a decent pace. Most multi-stroke pneumatic airguns are compact, recoilless and light weight. Multi-stroke pneumatics are moderate in power. The big down side to a multi-stroke pneumatic is all the time and effort needed to get a shot off, and a second shot is near impossible before your quarry runs or flies away. As you pump up the multi-stroke airgun each progressive pump takes more effort. Accuracy from a multi-stroke is just OK. There are too many variable in the pumping procedure to allow for stellar performance aside from the human error. A more preferable form of pneumatic is the single stroke pneumatic airgun. As the name implies, one motion of the cocking lever is all that is needed to compress the air for propulsion. The single stoke format is used on many high end 10 meter match airguns, such as the Beeman/FWB 601. Consistency, accuracy and lack of recoil are the reasons top shooters gravitate to this type of power plant. The downside is lowish power, but with tack driving accuracy at close range, again the reason 10 meter shooters love them. The third type of pneumatic airgun is the pre-charged pneumatic. This is the best of both worlds. You can get variable power from low to high if you want it. Incredible accuracy, easy cocking, and no recoil and lots of shots from an air charge. The charge take little effort on your part because the air is compressed at the dive shop into a SCUBA tank. All you need to do is siphon some of the 3000 psi out of the SCUBA tank and into the airgun via a special hose with a pressure gauge. Pre-charged pneumatics come as competition airguns for the field target set, and lightweight hunters for those so inclined. Some of the pre- charged airguns are multiple shot repeaters so the airgun hunter with poor aim can get a second chance with no pumping.

Spring-Piston Airguns

When someone says airgun these days they probably mean a spring-piston airgun thanks to Dr. Robert D. Beeman's relationship with Weihrauch and Feinwerkbau, two of the best and most prolific makers of high quality spring- piston airguns over the years. Spring-piston airguns are the easiest airguns to shoot, maintain and own. The spring-piston gun most shooters cut their teeth on 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 and now you are 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 be breaking the barrel, cocking an underlever, a side lever, or a top lever (overlever). Inside they are basically the same in principle. Things like spring rates, diameter of the compression tube (receiver) and swept area can be different depending on the gun designers ideas. 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. What happens when this error occurs? The piston head is smashed into the front of the receiver (compression tube) 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. Do not worry. A spring piston replacement and piston seal change are relatively cheap and very easy for an airgun smith to accomplish, but again we are talking years of use and thousands of pellets. 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

As their name implies, these airguns are powered by CO2 as a power plant for an airgun is kind of funny because 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 airguns can and will change. You wonder with this point of impact change situation why would these serious match shooters choose the CO2 propulsion system to break records. Well, these people are smart. They bring their CO2 airguns to the range, let the airguns stabilize to the ambient temperature in the range and sight in. Right-left (windage) point of impact will be constant, your up- down (elevation) zero will very slightly until you sight in. 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.

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