Spring-piston air guns are able to achieve muzzle
velocities near the speed of sound from a single stroke of a cocking
lever or the barrel itself. The difficulty of the cocking stroke is
usually related to the power of the gun, with higher muzzle velocities
requiring greater cocking effort. An older single shot spring-piston
air gun. Spring-piston guns operate by means of a spring-loaded piston
in a chamber separate from the barrel.
Cocking the gun compresses the
spring; pulling the trigger releases it and causes the piston to
compress air in the chamber directly behind the pellet. The spring is
usually made in the form of a steel coil. As the air is compressed it
increases in temperature (Charles' Law) becoming very hot, possibly in
excess of 1000 °C. Because of the rapidity of the firing
process,
very little of this heat is lost into the gun's metal parts (see
adiabatic process). Consequently, spring-piston guns are more efficient
than reservoir guns.
Modern air gun lubricants (such as molybdenum disulfide)
are generally designed so that they do not burn at this temperature.
Before the availability of synthetic lubricants, when petroleum based
products were used, upwards of 30% of the energy of the shot may have
come from the burning or "dieseling" of some of the lubricant,
according to some writers. The use of such combustible lubricants in
modern guns, which are much more highly stressed, can severely damage
the spring and piston seals.
Spring-piston guns seem to have a practical upper limit
of 1200 ft/s (370 m/s) for .177 cal (4.5 mm) pellets. Higher velocities
cause unstable pellet flight and loss of accuracy. Drag increases
rapidly as pellets are pushed past the speed of sound, so it is
generally better to increase pellet weight to keep velocities subsonic
in high-powered guns.
Most spring piston guns are single shot breech
loaders by nature (somewhat like an old shotgun) but multiple-shot guns
have been increasingly common in recent years. Spring guns are
typically cocked by a mechanism requiring the gun to be hinged at the
mid-point (called a break barrel), with the barrel serving as a cocking
lever. Other systems that are used include side levers, under-barrel
levers, and motorized cocking, powered by a rechargeable battery.
The spring in a spring piston air gun is very powerful
and is held back by a sear that has a very small engagement area. There
have been cases of severe crushing and even amputation when the spring
has been released unexpectedly. Spring piston shooters should always
use one hand to restrain the cocking lever when loading these guns so
that should the sear slip, they will not be injured.
Spring guns,
especially the higher powered ones, have a significant recoil resulting
from the forward motion of the piston. Although this recoil is less
than that of a cartridge firearm, it can make the gun difficult to
shoot accurately as the recoil forces are well under way while the
pellet is still traveling down the barrel.
Most guns seem to respond well to a light, repeatable
grip that allows the gun to vibrate the same way from shot to shot.
Spring gun recoil also has a sharp forward component, caused by the
piston as it hits the forward end of the chamber when the spring behind
it reaches full expansion.
This sudden forward acceleration helps to
counteract the backward recoil, since the backward and forward recoil
forces happen within milliseconds of each other, but it is infamous for
knocking around and loosening the lenses and reticles found in
telescopic sights, even those which are designed to withstand the
(backward-only) recoil from high-powered firearms. On any but the
lowest power spring guns, any mounted telescope should be airgun-rated.
AirSoft Spring Air Guns
are styled after some of the world's
most famous firearms. Spring Air Powered handguns are true to scale and
easy to operate. How they work...Pull back the slide (just like the
real firearm they are modeled after) to charge the firing
mechanism...Aim and fire. Spring Air models must be manually cocked
each and every shot. Because of their maintenance free design and
affordability these are excellent entry level AirSoft guns for the
hobby and recreational enthusiast.
