NPAS

NPAS (Negative Pressure Adjustable System) is an adjustable power regulation system used in gas-powered guns with GBB (Gas Blowback) operation. In practice, it is a special nozzle or valve in the gun’s bolt that allows fine adjustment of the amount of gas flowing from the magazine valve into the barrel. This makes it possible to control both the muzzle velocity (FPS/Joule) and the strength of the blowback.

History and origin of NPAS:

The first NPAS systems started appearing in GBBR (Gas Blowback Rifle) replicas from brands such as WE-Tech, RA-Tech, and GHK.
The goal was to allow players to legally and easily regulate power according to the limits of specific airsoft events and countries.
Before NPAS, players had to change entire valves, nozzles, or even magazines, which was expensive and impractical.

How does NPAS work?

Inside the nozzle, there is an adjustable valve that regulates gas flow.
When opened more, the valve lets more gas through → higher muzzle velocity, stronger blowback.
When tightened, the valve reduces the flow → lower power, less stress on parts.
Adjustment is usually done with an Allen key through the nozzle or from the gun’s bolt.

Advantages of the NPAS system:

Versatility: Allows play in CQB (lower limits) and outdoor games (higher limits) without swapping parts.
Easy regulation: Adjustment can be done within seconds.
Parts protection: At lower power, the bolt and other components wear less.
Precision: High-quality NPAS systems allow very fine tuning (e.g. 5–10 FPS difference).

Disadvantages of the NPAS system:

More complex design: More moving parts → risk of malfunction or leakage.
Power fluctuation: Settings can be affected by temperature and gas type (Green Gas, Red Gas, CO2).
Higher maintenance: Requires regular cleaning and lubrication to maintain functionality.