Stan;
That is pretty much in the same range as the easy-flow I mentioned. With that much silver content, it would be considered a true silver solder. I don't recall now if Force 44 or the Eutectic I mentioned have any silver at all or not, but if so probably no more than a % or so. Many people call these silver solders but in reality, they are not.
Yes, I have done some "Small" jobs with the easy-flow even using a propane torch But doubt one would have much luck repairing that breech rib extension with one. Just too much mass there to heat. As to just how hot the flame burns is not the whole story, you also on larger work have to have enough Volume of flame. I have a little Pencil Torch that is refilled with Butane same as grill lighters. The flame itself is plenty Hot but so tiny that for anything with much mass to it the heat will simply dissipate faster than it can be put in.
