Large Bore Rolling Block of Unknown Origin

[Patrick Chadwick]

I apologize if I am unnecessarily pessimistic, but the block end of the chamber looks like an awful fudge. There does not seem to be a recess for a cartridge rim, and there are several grooves/scrapes in the chamber wall as well. They could amost be relics of rifling. The block, on the other hand, looks OK.

Is there a proper chamber cut in there, or has someone simply taken an overlong barrel from heaven knows where and graunched it into the receiver housing?