JSB exact diabolo 8.4 and that was with a full fill of 3000psi to almost empty it's regulated at 1500psi so I can't go under 1500psi.
and yes if anyone want's to test this I willing to let you or them do it. but you got to re fill me tank after. pump it up.
I fillled the tank on my air gun so the airgun chamber made the air tanks bigger I'm sure that help and I have a drop down tank block too.
I'm very happy with my QB best airgun I ever had or modded. but we did have some problems lol.