A buddy of mine wanted to get an old rolling block carbine back into the woods but the bad 43 cal barrel had to go. The gun had been reblued at some point and the internals were not molested at all from their original Remington factory fit & function, so it was a fine candidate for a 45-70 conversion. I told him to pick up a nice Ebay barrel at some point and he did just that with the purchase of a Ruger #3 45-70 barrel that was a mint factory take off. I told him the big RB receiver ring can "sleeve in" about any factory barrel from what ever. So, In this shot, what you see is the original square 12 TPI shank cut off and taped with a 15/16ths x 16 TPI internal thread. Once that was done, the Ruger .900 OD 16 TPI shank was turned down to .875 and then lathe turned treads to a hand fit zero wobble fit to the old shank bushing. The trick was to set the old shank extractor cut to clock right in the receiver while at the same time, the Ruger barrel sights clock at 12 clock over the receiver. Once the proper bushing position was set and marked, The bushing gets JB welded to that exact spot.
Then the shank gets the breach block clearance cut and extractor cut via the original shank cut position into the Ruger steel.
Here the extractor has been mig welded to its needed extra length after the original chamber was deepened to perfect head space. The cold blue still shows the slight face line of the Ruger barrel in the core of the original shank face.
A 1976 made Ruger tube....