Tin around here is too expensive to use much of. I always use straight clip on WW, but for hunting bullets I use 50/50 pure lead/WW and 2% tin. Makes a very good performing bullet.
I have never used it, but I think allota guys use pure lead-tin in 10-1, 16-1 and 20-1 depending on what gun they are shooting.
I might be wrong, but I think most of the old "pre jacketed" guns shot 20-1 and 30-1.
A good friend of mine is a collector of the old guns. I asked him once his alloy for 45-70 and he said just pure lead with a little tin. He didnt even weigh the amounts. It worked fin for him.