I use the Missouri Bullet Company's 158gr SWC.
They're back ordered but worth waiting for.
Missouri Bullet Company
Just understand too hard a bullet pushed with too little pressure will lead the barrel as much or more than to soft a bullet pushed with too much pressure.
Plus one for Missouri Bullet Co., I use thier .357 Action SWC bullet's with good accuracy and miminal leading at Mag velocitys. Thier .38 Match SWC bullets work quite well at .38 Special velocitys. They tune the bullet alloy to the expected use of each bullet and so far so good.
Going back to when I first started casting bullets for .357 Mag:
a 10-14BHN alloy was HARD. A properly sized bullet was all you needed with this alloy. Many used gas-checks, but this wasn't needed if you had a good revolver--where the throats in the cylinder had to be large enough that the bullet was a tight/snug fit in the chambers (but no so small that the bullets were swaged down in size) and a barrel where the groove diameter was at least 0.001" smaller than the bullet diameter. At that time, this was not always true and many revolvers could not shoot lead bullets well.
So, first check your revolver to be sure it is cast-lead compatible before you start.
Next, today's HARD bullets are not required for a properly chambered .357 Mag. If not properly chambered, any alloy, no matter how hard, may not be adequate.
Well, that seems to be the current thinking but that has not been my experience. What needs attention is correct size and enough of a good lubricant. I have never had a correctly sized & lubed bullet lead a clean bore regardless of hardness.
This notion that you need alloys of three different hardnesses for bullet used in 700, 1000 and 1300 fps loads is a pile of horse dung. Let's not make this more complicated than it needs to be. You don't need to do an algebra equation on a pocket calculator to determine the "correct BHN" in order to cast high quality bullets. Accurately determine and control the required size and lube and your good to go. Use a single alloy of sufficient hardness (strength) for all applications and get to loading & shooting.
Bruce