A paintball bottle as low pressure buffertank is pure waste of weight. For that there are better solutions.

And, if we keep the 4 liter per action, A 12 oz bottle contains 190 liter of gas @1 bar. 47 actions @10bar, lets say 35 real life.

A 9 oz bottle contains 138 liter of gas. Thats 34 actions op paper. 25 real life.

Lower the pressure to 6 bar, and the equation changes equaly.