We were only sidetracked cuz the original article (as well as apparently a few here) believed cannon, et al, are not included in the 2ndA.
So now we have to explain to every1 that ANYTHING is included in "arms"!
May be unimaginable esp. w/today's giant weaponry, but it has to be true! Otherwise we'd never be able to overthrow a big gov like this if we have to face their airborne bombing attacks w/a bunch of "small-arms fire"! I'm quite positive the Founders, fresh from experiences precipitating and during the RevWar, intended we should as a people be able to separate and that that would mean whatever means possible. FGS, it was a REVOLUTION against a GOVERNMENT! Why can't people understand that?
No "arm" should be withheld from the citizenry except for those that, by their nature, pose a danger to the community. In this category I put NBC weapons (nuclear, biological and chemical for the folks in Rio Linda). Even governments have a hard time keeping this stuff under control. You'll see siren towers erected across communities that have such storage at local armories to warn of containment failure. Certainly the Smiths don't want the Joneses to have NBC storage next door...
Other than that standard, no limits.