Can't believe I didn't reply to this when you posted (didn't see it, probably). So first of all, sweet job! Beats my little 1377-base rifle any day of the week...
Can you give a comparison between the tube material and thickness of the tubing you used and the standard tubing for a 22xx? All I have been able to dig up is an OD of 7/8" for the 22xx tube. Of course, since you didn't start with a 2240, I'm guessing you don't know offhand. I even tried looking for the o-ring sizes on some custom parts which fit in a 22xx tube, but they don't list them, of course.
I'm looking at implementing something like this with a much lower shot per fill count, but with parts purchased from Mountain Air, and some reinforcing of the valve in the tube. I was planning on using Walter's method of securing the valve (if you don't browse the Crosman forums, it's simply using some countersunk screws with the heads in shear with the valve tube and body), although I believe I'll have to borrow a better drill press or outsource the work to a machine shop.
Again, great job!
EDIT: forgot to mention I would be using CO<sub>2</sub> pressures of 1200 PSI max.
EDIT II: Well, as luck would have it, I found the dimensions I was looking for right after bumping a nearly year old topic. 7/8" OD, 0.65" wall. By my rudimentary calculations it should be fine at 1200 PSI, although a simple hydrotest would be in order to test my valve security...
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). Its reduced diameter ends sit through the transfer port and breech port and are held in place by the connection between the breech and gas tube themselves.
