At least all the shotgun only zones I've heard of also allow muzzle loaders... STUPID! Today's muzzle loaders are reaching velocities of magnum rifles. The restricting laws are TOTALY out-dated, and either need refining, or done away with. I actually vote for refining, because people are to stupid to not shoot 458 magnums at rabbits when houses are in plane sight.
Same thing applies to rimfires for squirrel. The velocities being hit with rimfires is giving them equal range as anything else, and very few have enough brains and patience to consider whats on the other side of their targets.
Eric, I think your "Magnum Whoop Ass .410 Slug" idea is 100% viable, and would pull a giant segment of the market. SO LONG AS they came out with some kind of futuristic looking, black, semi-auto that was "built to purpose". Then use that gun in a hit movie. SADLY, that's what drives the market.

And thats what would sway people away from other options, more than its performance.