I dunno if this helps but I pulled this from AM's site from the manual on the Diadem.
"The Diadem should get over 900 shots from a full 45ci/3000psi Nitro tank out of the box. Any modifications, such as changing the barrel, will change this number. Weather conditions may also affect the air usage. The paint itself plays a large factor in air efficiency – the better the paint matches the internal diameter of the barrel the better your air efficiency will be."
To see the full manual go here: