That is quite a variety of bore dia's. The ones I read were .763 and Mr Researcher says his largest is .790. My barrels are marked LLH or maybe LHH on the underside of the chambers. I don't remember exact and the gun is put away.I read some where that was a barrel maker in Europe that was used by many Amerivan gun mfr's. If any of you are shooting your 2 7.8 guns are you using RSt shells or rolling your own in brass or plastic?