Types Of Airguns
The hunter who wishes to take to the woods with an airgun has a wide choice of suitable rifles. Each type has several advantages and disadvantages. This brief description is intended more for the novice than the expert to help him or her choose a tool suitable for the task.
The variable pump air rifle is a classic. Because the number of strokes can be varied and the air is under high pressure, variable pump rifles have the advantage of offering the shooter variable power. The forearm serves as the pump handle so there is no external device required but a considerable amount of work is required to pump the rifle eight or ten times (usually the maximum number recommended). These rifles tend to be short and light for the power they achieve. The major disadvantage of the variable pump as a hunting rifle is that reloading is slow and a great deal of movement is required during the process. To pump the rifle, it is necessary to grip it in the middle so that one hand applies pressure to the gun in opposition to the pumping action by the other. This can be somewhat awkward if a scope is mounted on the rifle. Many hunters who use air rifles started with a variable pump and such a rifle is still a good choice.
In recent years, the popularity of spring piston rifles has increased enormously. However, rather than using the barrel as the cocking lever, other means of cocking the rifle have been devised. One variant of the spring piston design is the side lever rifle which utilizes a hinged lever along side the rifle as a lever that is pulled outward to compress air while leaving the barrel in a fixed, rigid position. Another fixed barrel design known as the under lever utilizes a rod held under the barrel as a cocking lever. It is pulled downward to cock the rifle. The essential feature is that the cocking motion pulls a piston to the rear inside the receiver while compressing a spring. Many rifles of this type can drive pellets at velocities up to 1,000 ft/sec or substantially more in .177 caliber if lightweight alloy pellets are used.
Break action rifles are widely used in hunting because they produce high velocity. Firing a break action rifle in which a strong, heavy spring pushes a piston forward to compress air results in movement of the rifle before the pellet leaves the barrel. For this reason, many shooters find that it requires a great deal more practice to shoot such rifles accurately. In general, break action rifles tend to be heavy, long, and noisy with a pronounced “twang” upon firing. The Crosman Nitro Piston® in which nitrogen gas is compressed rather than a spring reduces these undesirable characteristics of the break action rifles. The result is a rifle that has the desirable traits of a break action but one that is lighter, quieter, and easier to fire accurately.
A recent innovation introduced by Crosman is the Nitro Piston® power plant in which cocking the rifle moves a piston to the rear, but instead of compressing a spring, a gas (nitrogen) in a cylinder is compressed. When the rifle is fired, the compressed gas propels a piston forward to compress air in the receiver behind the projectile. The advantages of the compressed gas as a power source (sometimes called a gas ram) include lighter weight, a great reduction in noise and vibration, and the option to leave the rifle cocked for extended periods which might cause weakening of a spring.
Nitro Piston 2
Crosman expanded its lead in gas piston technology in 2014 with the introduction of the Nitro Piston 2. The design has several improvements that collectively increase speed while continuing to manage noise, recoil and accuracy. All metal-to-metal contact was eliminated and the piston itself was split to accommodate a bushing that acts as a brake at the end of the stroke, vastly reducing vibration. An additional consequence of the design is an impressive reduction in the effort required to cock the rifle.
Precharged Pneumatic (PCP)
The idea of pumping air into a rather large reservoir in a rifle (precharging it) and allowing only part of it to escape when the rifle is fired has been utilized for a very long time. The advantages of such a precharged pneumatic (PCP) rifle are obvious. Reloading is rapid and essentially noiseless, only air moves at the time of firing, and there is no need for a long receiver in which a piston moves. The reservoir may be left filled if desired so the rifle can be ready for quick use. The disadvantage is that the reservoir must be filled in some way with the most common way being by means of a special pump. A large number of pump strokes are required to fill a reservoir to a pressure of 2000-3000 psi. After the reservoir is filled, up to 25-30 shots can be fired without having to recharge the rifle. Another disadvantage is that unless the filled reservoir provides power for a sufficient number of shots for the hunt, a pump must be taken along.
Precharged rifles are generally very powerful and also accurate as a result of their fixed barrel design. The fact that only air moves when the rifle is fired also contributes to outstanding accuracy. Consequently, PCP rifles are the choice of many serious airgun hunters, and the single shot Benjamin Discovery and the repeating bolt action Marauder are examples of this type of rifle.
Although the internal pressure in a CO2 rifle is limited to the pressure produced by the vaporizing CO2, that pressure is sufficiently high to drive pellets at approximately 600-700 ft/sec making the rifles powerful enough for use in hunting small species. One advantage of this type of rifle is that the CO2 cylinder holds enough gas to give a series of shots that can be fired simply by loading only the projectile. Such rifles are quick and quiet to reload and require a minimum of movement which may be an important factor in some hunting situations. These characteristics are shared with the PCP rifles in which the reservoir holds enough compressed air for firing several shots. The CO2 cylinders are small and light enough to carry several while hunting.
Jim House began shooting with a single shot BB gun at a very early age. Now, seventy years later, he is an airgun enthusiast. After a 32-year career as a chemistry professor at Illinois State University, he has written extensively about shooting sports, which has resulted in the books American Air Rifles and CO2 Pistols and Rifles. His books also include The Gun Digest Book of 22 Rimfire and, with his wife Kathleen, Customize the Ruger 10/22. Jim is the Reloading Editor for Gun World magazine and a Contributing Editor for The Varmint Hunter Magazine, The Backwoodsman, Airgun Hobbyist, and The Illinois Shooter. Although a lot of his work is with firearms, he maintains a keen interest in airgunning while also serving as Adjunct Professor of Chemistry at Illinois Wesleyan University.