Airgun Glossary of Terms

Term / Abbreviation Definition

Adult Airguns

Elitist colloquialism for airguns intended for the discerning "Adult" market. Such guns are too powerful, too heavy, too large or too expensive for the youth and beginner markets.

Adult airguns guns are manufactured from the finest materials finished to the highest standards. Shooting accuracy, reliability and pride of ownership are expectations of these airguns.

BB

Popular projectile in the US; literally a steel Ball Bearing, usually copper coated.

In Europe, usually a lead or similar soft metal round ball.

Steel BB’s weigh 5.42gr (0.35g); lead BB’s weigh about 8gr (0.52g).

Lead balls are slightly larger (0.17") than steel BB’s (0.16"). It is never wise to shoot steel BB’s in European made airguns unless specifically recommended by the manufacturer. Especially be careful with piston airguns because the BB may be undersized and will not cushion the piston slamming home. They may also cause damage to the rifling. Lead balls are usually quite acceptable if they are a push fit in the barrel and can give good accuracy. They are much easier to load than the traditional pellet.

BB Gun

Traditionally American. Usually a "toy" gun that shoots BB’s usually intended for youths and carnivals. Rarely applicable to "Adult" airguns.

In recent years a number of European rapid fire CO2 pistols have appeared. Most use lead ball ammunition; some use steel BB’s.

CO2 Gun

Airgun powered by Carbon Dioxide (CO2) from a compressed liquid source.

CO2 boils from a liquid state to a gas as the gun is charged. Gaseous CO2 propels the projectile when the gun is fired. Usually multi shot per charge of CO2.

CO2 typically produces 500 psi at 32F (0C) and 1000 psi at 85F (29C). This provides a typical operating pressure of 750 psi in airguns.

The temperature – pressure sensitivity poses design and performance problems for guns used outdoors; very well suited for indoor shooting in a temperature-controlled environment. Shooting many shots rapidly causes the boiling gas to reduce the temperature of the reservoir and thus lowers the pressure.

A favorite power source for inexpensive airguns and repeater action replica guns, especially pistols is the Crosman "Powerlet" / CO2 12 gram bulb. These CO2 bulbs are very convenient power sources but are relatively expensive compared to "bulk CO2" decanted from large containers into a reservoir in the airgun.

Match grade CO2 guns typically use bulk CO2 and may have bulb capability as a backup.

Competition / Match Grade airguns

The pinnacle of modern airguns for precision and shooting balance. The class of airguns used in Olympic competition. Exceptional accuracy with modest power.

Competition air rifles usually produce 5fp to 6fp (6.78J to 8.13J) muzzle energy. Pistols usually produce 3fp to 4.2fp (4.07J to 5.69J). Accuracy measured in hair widths.

Favored power systems are PCP, single-stroke pneumatic and bulk CO2. "Recoilless" spring powerplants have largely gone out of fashion.

FAC

British Fire Arm Certificate. Required for any air rifle in the UK producing over 12fp (16.27J). The majority of British and European air rifles are designed to this limit. FAC for pistols is 6fp (8.13J).

fp

Foot Pound: measure of energy (work). Metric: Joule (J).

1 fp = 1.3558 J

A foot pound is the amount of energy required to lift one pound weight one foot off the floor.

Fps

Feet Per Second: measure of speed. Metric: Metres per Second (mps).

1 fps = 0.3048 mps.

We commonly refer to "fps" as velocity. Velocity is a vector quantity, the rate of change of position in a given direction. Whilst the projectile has velocity, all we can measure and report is speed, that is: the time taken to travel between points.

Gas Strut (US: Gas Ram)

The gas strut was pioneered by Theoben in the UK and they supply them for after-market conversions of several models of UK and German HW air rifles.

The strut consists of a rod and piston in a pressurised, sealed chamber. It replaces the steel spring in piston airguns.

The compression and release characteristics of the gas strut are different to the traditional spring. Most noticeable are: less mechanical noise during cocking and discharge; less perceived piston bounce and "recoil"; and possibly longer service life than a spring.

Gas strut units are usually two to three times the cost of a good quality steel spring and the overall benefits are debatable. My BSA Supersport was "smoothened" considerably by fitting a Theoben gas strut.

gr

Grain: measure of weight. 7000 gr per pound. Metric: Gram (G)

1 gr = 0.065 g

Magnum Airgun

Colloquialism for any air rifle producing something over 10fp (13.56J) of muzzle energy.

The typical US advertising measure was the airgun should capable of driving a pellet over 1000 fps. It has usually proven difficult to find a flea weight pellet capable of attaining 1000 fps with reliability and accuracy.

Another interpretation of the term is for "export" models of European air rifles that are originally designed for 12fp, but have been tuned to provide a few more foot pounds for the US market.

Muzzle Energy

The energy of a projectile as it departs from the muzzle of a gun. Derived from the formula: 0.5 x mass x velocity squared.

Units are fp (foot pounds) or J (Joules).

Muzzle energies may range from 0.5fp (0.65J) for inexpensive BB pistols, to 5.5fp (7.46J) for sporting spring pistols and competition rifles and up to 40fp (54.23J) for extremely powerful PCP sporting rifles. The majority of European sporting air rifles are legally limited to 12fp (16.27J) with US export versions ranging up to 16fp (21.69J). FAC rated British airguns are rated at between 20fp (27.12J) and 30fp (40.67J).

PCP Airgun

Pre-Charged-Pneumatic airgun. The projectile is propelled by compressed air supplied from a high pressure reservoir charged from a SCUBA tank, hand pump or other external source. Compressed air is released when the gun is fired. Usually multi shot per charge of air. Many are fitted with multi-pellet magazines.

Operating air pressure is usually between 2000psi to 3000psi (13788kPa to 20682kPa) from a SCUBA tank charge.

The most powerful modern airguns are PCP’s. It is also a favorite energy source for Competition / Match grade pistols and rifles because of the consistency and ease of use between shots. There is practically no recoil to upset the shooter.

The major disadvantage (besides charging with air) is relatively high noise. Sound moderators are commonly fitted where legally allowed.

Pellet

A lead or soft, heavy alloy projectile, typically of a "Diabolo" or waisted / shuttlecock shape.

psi

Pounds per square inch: measure of pressure. Metric: Pascal (Pa) or Kilopascal (kPa)

1 psi = 6894.7 Pa or 6.894 kPa.

Pump-Up Gun

Airgun powered by air compressed by a pump integral to the gun. Usually all of the compressed air is discharged when the gun is fired for a single shot per air charge.

Rifling

Grooves and lands forming a longitudinal twist down the barrel of a gun. Such guns are called rifles. Pistols most usually have a rifled barrel, however, many rapid fire air pistols are "smooth bore" (i.e. not rifled) because they shoot BB’s or lead balls.

Slug

Vernacular for Pellet. Originally may have referred to lead projectiles of a blunt bullet shape, similar shape to "slugs" used in shotguns.

The "slug" shape has reappeared in the contemporary "Dynamic" non-lead airgun projectiles.

Spring Gun (also: Piston Gun)

Airgun powered by a compressed metal spring or gas strut driving a piston, which is usually cocked in a single stroke. Some variable cocking stroke piston airguns are available. Some may have multi-shot magazines. All are single shot per piston release.

The major disadvantage is spring "recoil" or piston jump on discharge occurring before the pellet has left the muzzle. This can upset accuracy and discourage novices.

Youth Airguns

Colloquialism for airguns intended for the youth or novice market. Such guns are characterized by low cost, lightweight, smaller frames and stocks and are easy to cock and load by someone of smaller stature. Typified by BB and pellet guns of low to moderate muzzle energies.