Gary, Assuming these are a set you put together. They would typically be soldered at the muzzle and at the breech, with a gap, the length of them, between the solder points. Kind of like someone that is bowlegged, standing at attention. The gap can be either squeezed together, or wedged apart, in order to bring both barrels impact point together at whatever yardage you think suitable. The sight placed to accommodate that point. If it is a difference in elevation then they will have to be taken apart and re-aligned. If they are existing barrels, you would have to remove the ribs and go through the same procedure. That, is a bear of a job! Good luck!
Robby