i use common lead. others like 2 or more percent antimoney for hardness.
Ray Beihler and Walt Astles recommended common lead.
A great primer is in their book. it should be available at a public Library.
Bullet makers believe a percent antimony is good because it "feels" better and doesn't coat punches. Don't know what I'm talking about but it sounds good...
Some use very soft lead because it is easier to form into cores. I was sort of interested to see that Hornady SX 22 caliber bullets use a much harder lead core than most others. I believe it depends on the thickness of the bullet jacket, thicker jackets using soft lead, thinner jackets using harder lead. As a experiment I ran up some bullets with 22 RF hull jackets. Some were made with soft lead cores, some with harder lead cores, and proceeded to load a few rounds of 22-250 with them. Some of the soft core bullets vaporized on their way to the target, but none of the harder lead core bullets did. I don't know if that was a valid analog to SX bullet jackets or not, but the outcome was certainly interesting. That may be sort of an answer to your question.....
We use 0.5% antimony, frankly because that is what we have always used. We tried 1% many years ago but I do not remember an appreciable difference. I also do not recall our testing methods being very scientific.
We use several type depending on use. i.e. rifle , pistol, rimfire, etc. I was just curious about the hand swage bullets, kicking around making my own short range BR bullets.
this is the benchrest forum, but i will tell you that most COMMERCIAL ammo has soft lead cores,,,i recycle some from an indoor range that allows no exposed lead bullets...so all the lead i get is core..it smelts in to very soft bricks,,,very soft...close to pure.
Yes, I want to make my own BR bullets, that's why I posted here on the BR Forums. And yes I know first hand what commercial mass produced bullets companies use. I make that choice on a regular basis.