q how are the barrels rotated a the rotational force is delivered by two hydraulic drive motors operating off of both main aircraft hydraulic systems a b the motors deliver their torque to gearbox in the hydraulic drive assembly this in turn delivers the force to two drive shafts the forward one goes to the rotor assembly on the gau itself while the second delivers it's power to the ammunition drum q how long is typical spin up time a while the system is capable of operating at rounds per minute it is limited to while installed in the aircraft since the gau has barrels it needs to spin at th of the firing rate basically since it's rotating a touch over rpm the spin up time is almost instantaneous on another point the statement on the gun gas on affecting the engines is complete rubbish during the firing of the gau the engines ingest so much gun gas that the engine igniters think super spark plugs must fire to ensure a stall does not occur the engines also will ingest so much soot from the firings that they need to be water washed have water and a mild cleaning solution misted into the engines while running at approx power periodically to remove soot from the blades anyone who has had to clean an a will tell you the gun gas goes just about everywhere aft of the nose