Airgun with selective bypass from high pressure reservoir to firing pressure reservoir

An airgun has a high pressure reservoir for providing a pressurized motive gas to a breech to fire a projectile. A regulator is intermediate the high pressure reservoir and a downstream firing pressure reservoir for providing a consistent regulated pressure of the motive gas in the firing pressure reservoir. The airgun includes a bypass line for selectively connecting the high pressure reservoir to the firing pressure reservoir, independently of the regulator. Thus, an operator can select a firing of the airgun with either a regulated gas pressure in the firing reservoir or the pressure of the high pressure reservoir.