Hello AkMike,

Yes, one listing said 50 cal, and another said a measured 52 cal. And there was a mention of 3-1/4" chamber measurements. The 12.0 mm stamping would indicate a .472 bore, but not sure what the groove would measure. I will find out for sure in a week or so.

Any idea of what the "MESSART" barrel marking is all about? The rifle's serial number is 184 so I believe the "3716" stamping is perhaps a Henry record license number. My W. Richards numbers are 2074 & 2075, dating to about 1872, so I would expect this higher number to be a later date.