I noticed that my M2 Impact was slowly losing air over time, I sprayed down with Windex and noticed air was slowly coming out of regulaor weep hole on RH side of gun, I removed bottle, removed trigger guard, air vented out of rest of gun when I removed bottle so I knew it was regulator rebuild time. Removed side plate to expose trigger, removed pin from PacMan, pulled trigger group out to gain access to regulator. Unscrewed reg adjust screw then screwed out regulator body, pulled out piston with belville washer stack using Ernest Rowe piston removal tool so I would not damage. Carefully removes belville stack and placed over screw temporarily to keep in correct order. Removed all five regulator O rings and noticed the one on piston was deformed as well as the one inside regulator body. The one on end of regulator body that seals when you screw body into action was also in bad shape. Replaced both small O rings on adjustment screw, I also inspected the O ring down inside acton regulator cavity and that one looked fine. Lubed all O rings sparingly upon assembly with Super lube synthetic grease. Reassembled everything and once again used Ernest Rowe handy reg piston insert tool to install and release piston with belville stack. I inspected piston tip for wear and all looked good. Screwed bottle on and pressurized, backed out adjustment screw and set regulator to 100 BAR, this is where my .25 with 720 Plenum likes it.Checked weep hole again and no more bubbles, filled to 250 BAR and let sit overnight and needle still right at 250 BAR so all good now. Mounted FX Chrony and set velocity back to 935 FPS with 25.4 JSB. very little variation. All good now. I got about three years out of this regulator since last rebuild.