new backpack chamber w/ "air magazine"

[knappengineering]

I am planning on making a new pneumatic which will have 2 large 2" chambers with a regulator in a backpack and a hose will go to the rest of the gun. The gun will use a blowgun as a valve because if i use a modded sprinkler i might have trouble w/ the diaphragm seating. (I have another gun that uses a modded sprinkler valve and the exhaust from the blowgun goes to a hose to a magazine which seems to work pretty well, i just need to make it so that it only fires one round at a time.) So back to the new gun i was talking about, i want to add an "air magazine" to it but i'm not sure how to do it since i wont have the exhaust from a sprinkler valve. have any suggestions? sorry for the long post, and thanks in advanced!