OK- so let me complicate this (Boyle's Law- you b@stard! I thought I left that behind 30 years ago in school...)

by these calculations, an 88cuft 3000psi tank has .43 cubic feet of air, then we have a 550cu in CF tank at 4500psi, or what works out to be .46 cubic feet of air. How might one figure out how much air must be removed for that CF tank to reach 3000psi? 50%?

The whole point to this of course is to calculate how many fills an "average" airgun reservoir of what- maybe (.00625 cubic feet at 3000psi on a 1" diameter reservoir that is 15" long)? can get before a 550cu in CF tank falls below 207bar (3000psi)- the idea being that people need to fill 300bar airguns, not 200bar airguns...

Applying these formulae without developing an aneurism, this .00625cuft reservoir should be approximately 37 fills to drop the 550cu in tank from 4500psi to 3000psi?