That alloy is very close to ideal if you water quench. Except I would personally use SILVER BEARING no lead plumbers solder, if you have to purchase. If you already have plumbers solder, use what you have, as the silver content is small. However it aids castibility considerably. Also, cut the tin to half a pound, to be sure it doesn't exceed antimony content, as doing so will cause rapid age softening.
A good test for hunting bullets which you want expansion with is to gouge it with a good dry thumnail. Your nails will have to be strong, and bone dry. At least a couple hours after washing or getting the hands wet. If you can dig in a little the alloy is hard enough to hold to gether quite well, (with antimony content low like this alloy). If you can't put a little gouge into it, it is quite likely too hard to hold a good mushroom. (The breakoff hardness (maximum suitable hardness) with low antimony alloys is 16 bhn.) but you'll need a hardness tester to know if your thumnail has reached its limit or the alloy is over 16 bhn.
If you try to shoot this alloy air cooled you'll have leading problems with any lube except LBT bullet lube, long before you reach a suitable hunting bullet speed with riflesl LBT lube will take it to about 2400 fps with decent hunting accuracy in an average quality rifle barrel. But the biggest problem with that speed is weight loss on impact. Take the hardness to about the limit of a dry thumbnail and You'll do well. Test your load on 10 inches or more of water with a piece of plank or plywood behind, shooting at close range, to see if your bullets can handle the impact at top velocity. If you don't get a good hole through the plank, but just a bunch of pieces, slow them down or harden them up. Test again at long range to see how far away you can shoot an animal and be sure of expansion. Heavy bullets are best at retaining velocity, as a general rule, with spitzers being the best, and they will expand if you do your homework. Flatnose and roundnose shed velocity faster, but are killing the instant they touch skin, whereas a spitzer pokes a pinhole until it gets expanded a little.
