Sound advice there. There is a point of diminishing returns when using tin as a hardener.
For pistol bullets I'm not terribly picky about alloy. Clip on wheel weights (COWW's), of which I still have a serious supply of - they're becoming difficult to find - get mixed at 50/50 with soft lead (some of which is admittedly suspect as to purity) with a healthy "pinch" of pure tin as a mold filler-outer. As you can imagine, the bhn fluctuates a bit, say in the 8-10bhn range, but that is entirely suitable for my pistol and revolver shooting as long as I mind final diameter for a good throat fit. .32, .38 Spl, and .45 ACP and Colt is about the extent of it - but I shoot a lot in those calibers and experience zero leading with excellent accuracy. I don't feel that strict adherence to a narrowly defined alloy is completely necessary. As long as it's good and bloody soft, I'm good to go.
The last time I dealt with leading was back in the bad old days of my cast bullet Dark Ages when like so many people I was convinced that the harder the better in order to defeat leading in the bore. I was resigned to dealing with that bugaboo as the price to pay for cheap shooting. Then I wised up and started paying strict attention to throat diameters and sized accordingly, and concurrently softened my alloys drastically. Think of a soft bullet as acting like a very efficient cork to bottle up the hot gasses behind it as it starts its journey from the cartridge case. It's those hot gasses which jet past the bullet in an ill-fitted situation that causes leading, and contribute to inaccuracy. My mentor way back then routinely shot .357's and .44 mags and his bullets were definitely on the soft end of the scale - and his lack of leading was an eye opener to me.
As an aside, a large part of my casting efforts today is for single shot target rifles using plain base bullets, and my alloy of choice is 1-30 tin/lead with some occasional 1-20. No antimony need apply. My .22 long rifle casting is 1-40 tin/lead. (Yes there are those of us who shoot our own .22 LR handloads. In my case by breech seating the bullet ahead of a charged case for ultimate accuracy. It pays to have a couple buckets full of empty primed brass in that regard.)
