all you really need to do is create a steel or brass (anything you can solder) riser that matches the circumferance of the pump tube to lift the breach/barrel up 5/16 .. 3/8 inch or so. recreate the same curve on top.
Match and drill the holes from the tube and breach.
Unsolder the barrel. clean all the solder out of that hole. Machine yer barrel blank to fit the hole. fit must be ooooh sooo precise. Create the porting using the orginal barrel as a guide. Decision time: you could solder it back in ala the original, or drill 3 holes (say .050) ahead of the loading port at the 8,12, and 4 oclock positions (or 120 degrees apart). small thin oring to seal.
The riser allows you to shroud the thing. You will need a barrel band for at least the muzzle. If you shroud it, you can put a bushing in the shroud to help center the barrel, and take some of the stress off the breah.
Downside? now the breach carries all the stress of the mechanical joint. the front barel band will help some. A center band wouldnt be all that hard to make and install. If you use something like Lundy's breach mounts, the scope adds to the aforementioned stress to yer joint
I have no way to machine steel or brass to the levels of precision necessary or we'd discussion build issues instead of bench racing it.
I would be willing to donate a 39x pump tube and breach. and some drawings that explain it more if some one can come up with the necessary machining skills, tooling and the other parts.
Aint afraid of the solder... just need some other bits and tools
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