Kraigwy ... well I just put up some dummy test rounds with the Fiocchi brass. Did like you suggest ... .30 Carbine FL die.
Then used a Lee powder-thru die to flare the case mouth. (had it lying around)
Then modified a spare .32-20 Seater die I had wasting away by unscrewing the stem cap and dropping a 3/4" long 1/4-20 Roundhead Machine Screw into the end and screwing the cap down tight (you have to now set the depth of seating with the die lock ring instead of the stem cap, but that's OK). The bullet I ended up using was a 100gr, .312" plated RNFP that I had for my H&R.
Then dug up an old .25-20WCF seating die that I had laying around from some other project I pirated the other dies for and that was just PERFECT for putting just the right amount of chamfer/taper on the case mouth. A nice, little bit; nothing like the "factory" rounds so I hope for a decent case life.
Then put the .30 M1 die (without decaping pin) back in the press and just ran the loaded round up into it about half the length of the "neck" area (as otherwise the case would stick with about an 1/8" not fitting into the cylinder). After that last, little operation the loaded rounds drop right into the cylinder and the case mouths snug up without any resistance when cocking the pistol.
Thanks for the tips ... now I can swing both ways on this cartridge!