Patw, I don't think I would play with the 32-20 brass as you described. If you can't get the carbine brass to work, why would the modified 32-20 brass work? ....and is it really worth the trouble? Carbine brass can be loaded over and over again. That 32-20 brass is pretty thin and you might get 2 loads from it despite all of the work you'd put into it.
Question: Are you loading military brass into your Blackhawk? I've gone through that for years and about 5 years ago I threw it all away or left if on the ground at the range. I only work with Remington brass now. I try to stay with one brand. Winchester or Remington will do fine. I use both standard brass and nickel plated brass. A friend of mine who also has a 30 carbine Blackhawk gave me all of his nickel plated brass because he had problems with it jamming up in his cylinder. It's a little tight in mine but I manage.
I have a suspicion (and I may be wrong here) that if your trimming to the correct length AND properly deburring the case mouths, then perhaps your sizing die may be the problem. A second suspicion may be in your brass itself. Are you loading brass that was fired from an actual M1 Carbine rifle? Sometimes the rifles can leave a burr on the case rim from the extractor banging into it. The distortion in the rim can lead to improper chambering in the old model Blackhawk since the rim itself seats into the cylinder recessing. A last suspicion lies in the gun cylinder. Is there any fouling on the headspace area in your cylinder? Check and see. Any residues can and will prevent your cartridges from seating correctly (and jamming against the inside of the frame when indexing).
Here is what I would try:
First, give your cylinder a full and complete cleaning in order that any old oil or fouling residues are removed. Once you've cleaned it....clean it again!
Then try seating some rounds. If that doesn't work, then I'd suggest buying 100 rounds of new Remington (or Winchester) brass and buying a new resizing die. (I'd probably get a new die anyway) Lee sells the complete set (carbide) pretty cheap. Resize the new brass fully, trim it, de-bur it, and load it. See what you get from there. Another thing to keep in mind is that although the die for the 30 carbine is or may be carbide, I find that I still need to use a little lubricant. Unlubed cases tend to take a lot of force to pull out of the die and sometimes the shell holder can pull the shape of the rim out of round. I find that to be the case often with 45 Colt ammo, so I always lube my brass (just a little) despite the use of a carbide die.
I have never loaded my 30 carbine rounds down to be honest. I always load to near full loads using either H-110, Winchester 296, or IMR 4227. Ironically, I've just begun looking into trying some loads using 2400 and Unique however.
If you are loading down just on account of the volume of the gun, perhaps you might try double hearing protection. My friend once used ear plugs inside his headset protection, especially when shooting indoors. Those little rounds can really shake a room when indoors! (It's funny how people come around and ask what you're shooting....only to show them this little, scrawny 30 cal. round.)
I've been shooting my old model Blackhawk for about 25 years. In fact, (ironically) it was the first handgun (other than a .22) that I purchased too. I shoot it often and take it out in the field a lot. Typically, I plink and hunt prairie dogs with mine and I've made some amazing shots with that thing, often times making over 100 yard kills with open sights. I've now mounted a scope on mine. Several years ago, with the scope mounted, I played around and tried to see exactly what that pistol can really do at a distance. I decided to try some long shots at some beer bottles and clay pigeons. (no, I wasn't drinking and shooting...the bottles were just available at the time) At 200 yards, resting on a sandbag, my first full cylinder full scored 3 pigeons and 2 bottles. I'd say that's more than what one would expect from a little round like the 30 carbine out of a pistol. In fact, that's probably better results than one would expect from an original M1 Carbine.
Good luck with your loading. I'm sure that you'll get that old Blackhawk working right....and when you do, ENJOY! They're a ton of fun!
