No guys, an Air Venturi Avenger is a 300 Bar fill gun. 4,000 is a bit conservative.
My 25 caliber does not do this but I've noticed over several shot strings that the velocity variation of some of them is > 30 fps. Not great. But that should not cause "wild" shots.
Is it possible the barrel is inadvertantly bumped in the fill process? The Avenger barrel is not supported at the muzzle end, it has a support at the action and about 2/3 of the way up but not at the muzzle. My DonnyFL adapter and the printed moderator I am currently using support the end of the barrel. That might be something to try. Just being extra carefull about the way the gun is handled during the next fill would also be something to try - that costs nothing.