The thing about 410 is yes there are three or four 00 buck pellets going at an acceptable rate for a handgun, but 00 buck has an extremely poor sectional density, each pellet winds up being less effective than what in today's society is considered the minimum one should carry, the 380acp, of cpurse I believe even a 25 acp is acceptable to carry, just as it was 40 years ago. What the 410 gains is you get either 3/4 misses or hits per shot. But again for a average person emptying 6 rounds accurately from a quality 380 like a sig 238 might take less time than doing 2 long double action pulls on the 410 wheel gun, most people have problems putting rounds on target quick and accurately with DA trigger pulls.
A single 00 pellet is only 55ish grains and closer to 32acp in diameter and performance, with 32acp ball having a slight edge on terminal and external ballistics. Considering it's fired from a revolver sized for 45LC that's just unacceptable to me, maybe you can be comfortable with that power to weight ratio but I am not.
The "spread", firing 00 at 5 meters all 4 pellets hit within inches, at least with the raging judge I tested.
The only reason the judge isn't an SBS under federal law is because the barrel is rifled and it's "designed" to fire a 45LC, it just happens to fire a 410 fine from the same chamber which is fine under federal law. California might have another definition of what's a handgun or short barrel shotgun or California bans a whole list of handguns by name, I wouldn't be surprised if the judge or governor was on that list. Actually if I recall correctly they have a list of what's approved for import to the state because they couldn't keep up with banning handguns by name.
Title 2 weapons(SBSs, SBSs, machine guns, suppressors) aren't hard to get, just a long wait, but travelling with them can be a nightmare, just driving cross-country is a hassle let alone full time traveling.
Interesting non-firearms can't be title 2. There's no tax stamp or wait for a 12ga side by side muzzle loader regardless of barrel length. And airguns now come with suppressors(Gamo I think is the one the ATF gave the go ahead to)