1377 HELP!!!!!

Hey everyone, I may have humped my self and am hoping someone here knows if I have a way out?
I picked up a 1377 in pretty good shape and may have slightly overpaid but not bad. PROBLEM lies in that a ordered a steel breech before it arrived and now find that I have an older "sliding cover" style pistol, all the breech kits say they will not work with these!!!!! So can I mod it or do I eat it?????
Thanks all,
Be well

Big Bore 44 said:

Only need three more pieces, New barrel, T-port, and T-port gasket. The old 1377s had a different feed angle and slightly different chamber length to the barrel.

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Thanks for the info! That being the case, at this point could I do a 22 conversion with a new barrel and bolt/probe?

Do I need a transfer port? I hear of something called an evo mod but can’t find any details, I think it has to do with the tp.