Is the term "solder" used interchangeably with "brazing" here?

Brazing, that is using a bronze alloy as the binding agent has a tensile strenght that approaches that of steel. Soldering has various grades, with silver solder being at the top, but still below brazing, and all the way down to very weak low temp solder used in electrical connections.

The way it was explained by an old gunmaker is that you use the strongest highest melting point binder, ie braze, for the main barrel joint, then go to a slightly less strong one for the loop and packing, and finally to a weak one for the ribs. That way there is no risk to the work done before from the use of flame, and also repairs are facilitated by not putting at risk the main bits, ie you can resolder barrels without affecting the loop, or the main barrel joint.

Brazing temperatures are in the 700 to 800 Centigrade region, which is close to the critical temp for steel, but can be controlled and not exceed it. Welding is a more drastic process in terms of local effects on steel.

The main question when it comes to barrels is why not base the design on a monobloc and avoid all the brazing-welding problems to begin with.