Yep. It's one of those counter-intuitive things. A bullet that fits the throat is your friend; if a bullet is too small and doesn't fit the throat no amount of extra hardness will prevent it from leading. A hard bullet that fits the throat certainly won't lead, but why waste precious tin/antimony (or the money to buy it)?
I wish I knew how that whole "hard cast" trend got started. (Well, I think I know how but will let it drop.)
Push a bullet through the throats of the revolver. If you feel good resistance with finger pressure you're ok. If they go through with no resistance get out your bore brush, you'll need it. Ignore barrel groove diameter, throats are what matter's (unless of course you have an oddball that was built with barrel groove diameter bigger than the throats in which case all bets are off accuracy-wise). You can certainly be more technical and drive a soft slug through the throat(s) and mic it and tell your bullet people that's exactly what diameter bullet you want. Additionally, make sure your expander button in the die expands the case mouth suitably too. Too small and the case itself will likely squeeze the carefully selected soft bullet down a bit, abrogating all your hard work.
Not entirely germane to revolver bullets, but I'm shooting very soft (1:20 and 1:25 tin:lead alloy) 200 grain GC'ed bullets through a .357 Maximum rifle. 1700+fps, regular old 50/50 NRA formula lube, zero leading and very good accuracy. Why/how? They fit the throat perfectly. Ditto my work with .32-40 schuetzen rifles - 1:30 and 1:40 alloys at 1400fps, and zero leading after literally hundreds of shots, again because of perfect bullet fit.
Last edited by gnoahhh; 11/20/22.
