More photos.
1) Breech end of barrels have been tinned with Hi-force 44 solder. Black crud is flux, yet to be washed off.

2) Muzzle end of barrels. I made this jig to hold the barrels over the Coleman stove for preheating.

3) Overall view. Jig also allows barrels to be rotated.

4) Ribs soldered in place.

5) Another view of same, with scope bases mortised into place and top surface matted with 50 LPI checkering file.

6) Overall view of completed barrel assembly.

7) Side view of front sight ramp, with top surface matted as well.

8) Another view of same.

9) View of muzzles showing regulating wedge soldered between the barrels.