PSI

PSI (pounds per square inch) is a unit of pressure used mainly in the USA and in technical fields where precise measurement of gas or fluid pressure is required. It indicates how much force (in pounds) acts on an area of one square inch. PSI is commonly used in air-powered weapons, HPA systems, pressure vessels, the automotive industry and also in airsoft when working with gases and pressure regulation.

Other pressure units and their differences

bar – the most common European unit; 1 bar ≈ 14.5 PSI.
kPa (kilopascal) – 1 bar = 100 kPa; SI unit widely used in science.
MPa – used for extremely high pressures (e.g. HPA tanks).

In simple terms:

1 bar ≈ 100 kPa ≈ 14.5 PSI

In airsoft, the most commonly used units are PSI and bar, because regulators, tanks and gas systems display them on their gauges.

Why is pressure important for airsoft gases?

Airsoft gases such as Green Gas, Red Gas and Black Gas have different pressures depending on their composition and the ambient temperature. The higher the gas pressure, the stronger the:

shot (higher muzzle velocity),
blowback effect on gas pistols,
stress on the weapon.

Gas pressure reacts directly to temperature:

in winter pressure drops → weaker shots, poor cycling,
in summer pressure rises → higher output, risk of wear or damage.

This is why choosing the right gas for the weather and the weapon’s construction is crucial. For example:

Green Gas – universal, medium pressure.
Red/Black Gas – high-pressure gases suitable for metal slides or cold weather.

Incorrect pressure can lead to worn seals, cracked slides or inconsistent performance.

Why is pressure the foundation of every HPA setup?

HPA systems operate using precisely regulated air pressure. The regulator maintains a constant PSI from the air tank, which provides:

extreme muzzle-velocity consistency,
fine-tuned power adjustment,
temperature independence (unlike Green Gas),
perfectly consistent shooting for DMR, CQB or Speedsoft.

A high-quality regulator is the heart of every HPA weapon. Some of the best include:

EPeS MaxFlow – extremely accurate, reliable, ideal for AEG-HPA conversions and as a primary regulator for systems like PolarStar, Mancraft and Wolverine. It offers minimal response time, stable pressure and is manufactured with precision in the Czech Republic.

Properly set HPA pressure (e.g. 70–120 PSI depending on the system) ensures:

stable Joule output,
accurate air dosing,
long weapon lifespan.