Solders are effectively a chemical bond where a liquid that cures bonds the two steel surfaces. An epoxy, or other glue joint is also a liquid that on curing forms a strong bond between the surfaces.

I did the calcs between solder and west systems epoxy on gluing a 22 liner barrel into a drilled out barrel. In terms of sheer strength the west systems epoxy is stronger than solder. And when you factor in the difficulties of making a good solder joint compared to an epoxy joint, epoxy wins.

I was happy using an epoxy with a c200°c softening point as in a 22 single shot you are not going to get a high temperature.

The late Victorian gunsmiths used all the latest technologies of their days. And they were quick to embrace new technologies as they became available. I am sure they would be embracing all the new technologies of today.