The Federalist and Anti-Federalist papers and the writings of Jefferson, Madison and others talks about citizen arms as a counter-balance against state and/or federal force. That tosses all the arguments about "proper weapons" right the heck out.
BUT, I don't view this as all that important. Reason being, I believe that in an insurgency situation, a good scoped bolt-gun in a real rifle caliber will be of much more use than an M4 with "da switch". A really good AR-10 variant in 308NATO/Win with a heavy barrel and a good scope might be even better, if it can reach out to 800yds or so - and the very best can. But a big mag won't mean a whole lot when the goal is "hit and run".
This is nothing new. We hurt the British the worst when we did hit-and-run with Kentucky Longrifles against their shorter-range, faster reloading Brown Bess smoothbores. We didn't hang around for them to reload in most cases - we got off one aimed shot at 200 yards they couldn't answer, they charged, we ran away. History could easily repeat itself.
Anybody who thinks a pitched battle with US forces on American soil would be a good idea is nuts. Long range rifles are the last practical gasp of the real 2nd Amendment. Fortunately the people who own and actually master such critters are serious martial artists and don't tend to go off half cocked mentally. That's a good thing. If things get bad enough to bring that crowd out to play, or even a small subset of that crowd, America would be a really ugly place to try and be a dictator to.
Remember: Saddam Hussein allowed a surprisingly large number of people personal ownership of full-auto AK-47s in Iraq. But he flat banned *anybody* having scoped bolt-guns - very few if any of his military had access to those and zero legally in private channels.
He wasn't *totally* nuts.