L23A1 gun questions

[teletech]

Sadly, the gun on my Scorpion met with a torch as part of bringing it across the ocean, but I'd love for it to at least look correct and function well enough to form the basis for a t-shirt cannon, and so I need some dimensions.

I guess the first place to start is does anyone have a set of prints for the breech assembly?  Failing that, knowing how long it is from front to back to a reasonable precision, say .010" would be enough to give me a running start.

Thanks,

[sterling1961]

Here is a link that might help

http://www.scorpiontank.co.uk/html/ContentsSummaryPgs/76mmGunSupport.html