Thank you for the input. There are no doubt cartridges that are better suited for non expanding cast bullets. But this is a special project with a very specific application.You likely don't need "hardcast". A softer bullet that fits will often shoot more accurately and won't lead the bore and will penetrate just fine for those who need a lot of penetration for whatever reason. I'm speaking of conventionally sized and lubed bullets. I've read that bullet hardness isn't as critical with coated bullets but I've had no experience with coated.
I seldom shoot 9mm anymore but did extensive cast bullet work with the cartridge in several pistols for many years, just to see if cast bullets were practical and accurate in the 9mm. I prefer heavy bullets. I tried around a dozen cast bullet designs and about that many powders. My long time favorite bullet for the 9mm has been the Lyman #358212, an obsolete .38 Special round nose that weighs about 150 grains cast of wheelweight alloy. I size to either .358" or .359" (I'd have to look at my notes to be sure). I use Bullseye powder, but HS-6 is a close second. These loads are accurate and shoot to point-of-aim at 25 yards. Functioning is perfect in my three 9mm pistols, all of which I've had more than thirty years: Beretta 92F, Sig P226, and a Walther P4.
I much prefer the .45 ACP over the 9mm, but the 9mm is certainly a good cast bullet cartridge for 9mm enthusiasts.