Don't take this the wrong way, but I can say as one of the uniform-wearing types out of DoD that the effort to ensure military personnel won't carry out grossly Unconstitutional orders is far more important for national liberty than guns.
Your automatic rifle may match up well to a soldier's, but it won't match up at all to crew-served weapons, JDAM laser-guided bombs, cruise missiles, tanks, etc.
And even more important than technology is training, logistics, organization, and discipline which is something that all branches of the military will kick a militia's ass up and down the coast with.
The militia was intended to be a way to defend America against foreign invasion without having to maintain a standing army, as a standing army was considered dangerous for liberty.
But the Second Amendment wasn't intended to be used to fight against the government, or a standing army. Which is well, since the standing army is here now, and better than you at fighting.
Instead we do all we can to ensure that everyone from E-1 to O-10 understand what they're fighting for (the Constitution, not the military), who is in charge (the civilians), and what constraints are placed on their domestic operations (e.g. Posse Comitatus). That way an order to do something illegal like establish martial law in a town (for non-"Title 32" forces) would be instantly recognized as abnormal and wrong.