Max fill pressure for the .58 is about 3800 psi, my tank was running low that day but was getting some really good velocities. At full pressure, the 820 grn Mr hollowpoint bullet shoots at about 700 fps... ALMOST 900 FPE!!! plenty of power. only con about the gun is that its heavy, I have a 30" barrel, and with scope, the rifle is probably pushing 14-15 lbs. Also, it takes about 50+ lbs force to cock and lock back the charging bolt. Fit and finish are excellent. very good bluing on the metal parts and I have a multi-color laminated sporter stock. At full pressure, you will get about 3 full power shots, then another say 3 usable shots for a round ball.