Spring-piston guns were the gun of choice in most of the Olympic air gun matches which took place in the 1970s and into the 1980s, while the Chinese army still uses spring-piston small arms to train more economically.
These guns have a coiled steel spring-loaded piston contained within a compression chamber but which is separate from the barrel. When the gun is cocked, the piston causes the spring to be compressed and small hook is engaged to keep it compressed, until it is released when the trigger is pulled. Then the spring decompresses and pushes the piston forwards which in turn compresses the air in a chamber behind the pellet. Once the pressure has risen sufficiently to overcome any static friction in the barrel, the pellet is propelled forward by the expanding column of air behind it.
This process takes only a fraction of a second during which time the compression of the air causes it to be heated to several hundred degrees. Thus lubricants must be used which will not ignite in the gun chamber at such elevated temperatures, although nearly all substances will burn to at least some extent.
Spring-piston guns generally seem to have a practical upper limit of 1200 ft/s (370 m/s) for .177 cal (4.5 mm) pellets. If the velocity exceeds this rate, the pellet can become unstable and accuracy is lost. Most spring piston guns can load only a single shot but multiple-shot guns have been increasingly common in recent years.
This type of air gun, especially the high-powered ones, has a significant recoil which, together with vibrations from the spring, can make the gun difficult to shoot accurately. However, a good quality spring air gun can have very long service life as it is simple to maintain and repair, and because it delivers the same energy on each shot, the trajectory is extremely consistent.
These guns have a coiled steel spring-loaded piston contained within a compression chamber but which is separate from the barrel. When the gun is cocked, the piston causes the spring to be compressed and small hook is engaged to keep it compressed, until it is released when the trigger is pulled. Then the spring decompresses and pushes the piston forwards which in turn compresses the air in a chamber behind the pellet. Once the pressure has risen sufficiently to overcome any static friction in the barrel, the pellet is propelled forward by the expanding column of air behind it.
This process takes only a fraction of a second during which time the compression of the air causes it to be heated to several hundred degrees. Thus lubricants must be used which will not ignite in the gun chamber at such elevated temperatures, although nearly all substances will burn to at least some extent.
Spring-piston guns generally seem to have a practical upper limit of 1200 ft/s (370 m/s) for .177 cal (4.5 mm) pellets. If the velocity exceeds this rate, the pellet can become unstable and accuracy is lost. Most spring piston guns can load only a single shot but multiple-shot guns have been increasingly common in recent years.
This type of air gun, especially the high-powered ones, has a significant recoil which, together with vibrations from the spring, can make the gun difficult to shoot accurately. However, a good quality spring air gun can have very long service life as it is simple to maintain and repair, and because it delivers the same energy on each shot, the trajectory is extremely consistent.