I'll respectfully disagree with you here.Here's what they should have done.
A .30 carbine snub that uses full moon clips.
Corbon even makes a .30 carbine dpx load.
The .30 Carbine round is a fairly good performer if you give it an 18" barrel.
Then it produces 1900 fps and gets you 882 ft-lbs at the muzzle. As a rifle, it's puny. As a handgun cartridge it wastes energy in muzzle flash (and a deafening report). As a carbine, it does okay. I happen to think the M1 Carbine is a good choice for home defense because it's small, light, nimble, powerful enough and can be used one-handed.
However, the .327 simply outperforms the .30 Carbine.
Out of a 3-inch barrel the 100-115 grain loads spec out to 1400 (435 ft-lbs) and 1330 (452 ft-lbs)fps respectively. That's equivalent to a hot 9mm or lower end .357 load. But if we put the .327 Magnum into an 18" barrel, the 100 & 115 grain loads produce much more horsepower. The 100gr load hits 2150 fps (1026 ft-lbs) and 1880 fps (903 ft-lbs).
In an 8" barrel, the .327 hits 1900 fps using American Eagle 100gr loads. No doubt with a little time, we'll see handloaders pushing 2000 fps from an 7.5-8" barrel as experience is gained.
Yes, I'm sure you can beat that with handloads in a Blackhawk. But allow the .327 community to work up similar loads for the BH or GP-100 and the gap will be narrow.
In a short barrel, the .327 is much more efficient than the .30 carbine because it uses faster powder. There is a lot of interest in the .327 in longer barrels -- 5½ to 7½" cowboy guns to 16" and 18" lever rifles. I think we'll eventually see "high-speed" or "rifle" bullets made for hunting with the .327 in a rifle where the JHP/JSP opens slower than the self-defense handgun bullet.