Very Large Volume Valve Posibilities?

[DavidS]

I am considering using a modified Crosman 66 pump tube in a Crosman 2289 build, and using the stock 13xx linkage, with an extended volume valve.    I am wondering what this could do for an ACP???

I would like to get somewhere in the range of 4 to 5 consistent shots possible between pumping, and somewhere in the area of 10FPE per shot.

I would use a cam-over pop-up pressure indicator to pump back to pressure once I figure out the pressure needed (and get the springs and hammer mass balanced out for consistency).

So has anyone attempted this?    And if so what is realistic to expect?   It will be a little bit before I get started, as I am waiting for my next 2289 to get here, though this is the time for a bit of research into the possible.