Allan Moon,
Unfortunately you choose to argue only those points which support your argument. Nobody would be foolish enough to argue that the tensile strength of silver solder is not greater than, say, Force- 44. That strength is not necessary in this aplication. If you continue to ignore the fact that the amount of heat required to do this job with a torch will change the strength of the steel, then you are free to flaunt your ignorance of even the basics of metallurgy to the world.

If one starts with a known alloy, knows its chemistry, is familiar with its properties, undertands what molecular changes occur in that alloy at 1350 degrees Fahrenheit, understands what heat treatment will be required after assembly, has access to a brazing furnace, and has access to a computer-controlled heat-treating furnace, then by all means, silver-solder to your heart's content. Unfortunately, the average guy contemplating a shotgun to rifle conversion has none of these luxuries. That is why a good Tin/Silver solder is the material of choice and yields a joint strength, if properly done, far in excess of that required. As I said earlier, Force-44 solder has a tensile strenth of 28,000, pounds per square inch. Calculate the surface area of the joint and you will find that the total joint strength is FAR in excess of the force generated by ANY rifle cartridge.

Tony, the failure in the Rigby rifle, to which Brown refers, was caused in large part by failure to pre-tin, and poor soldering technique, as I discussed in an earlier post. Ellis does discuss that very thing in the book.
Best,
Ron.