Why not make the inserts with an interference fit and press them in, as opposed to solder or adhesive?
Hope this helps.
Bill
In my experience, many machinists have problems managing to bore or machine a correct interference fit on beefy things like shafts for bearing races, and pump, motor, or line shaft couplings that are quite thick and only a few inches deep. Oftentimes, the installation doesn't go well, even when the shaft is chilled with dry ice or liquid nitrogen, and the incorrectly bored coupling is heated to expand the I.D.
If things get stuck in the process, then delicate precision tools like sledge hammers, rosebud torches, or hydraulic pullers are used to help separate things.
Getting a correct interference fit on two relatively thin walled tubes that are 18 inches long, and successfully pressing them into the ends of 28 or 30 inch long shotgun barrels is a recipe for disaster, especially if the fit is only a little bit too tight. I'm not saying this method wouldn't be possible, but the difficulty and potential for problems illustrates why even shorter rifled bore liners for pistols are secured with solder or an adhesive.
