I was just reading James Madison's notes towards his autobiography, published by Douglass Adair in The William & Mary Quarterly, vol. 2, pp. 191-209 (1945), and on p. 208 appears the following statement:
A Government resting on a minority, is an aristocracy not a Republic, and could not be safe with a numerical & physical force against it, without a standing Army, and enslaved press, and a disarmed populace.
Madison was writing in the early 1830s, but I have no reason to think that this was some then-recent epiphany of his — it seems to be a mirror of what appeared to be received wisdom at the time, from Blackstone to St. George Tucker to Story: A disarmed populace, the theory went, was an invitation to tyranny (or at least to aristocracy or monarchy); an armed populace would be an important bulwark against such tyranny. Federalist No. 46, also written by Madison, expressed a similar view; but Madison's statement in his autobiography makes the point more unambiguously, and in a context that seems a sincere and mature statement of one's views and not just a political tract aimed at an imminent political goal.
Nor was Madison writing about the importance of maintaining armed state-run and state-limited groups as a counterweight to the federal government. His statement seemed to refer to general political principles, applicable to unitary governments (such as each state, or such as England as described by Blackstone, who also described the English right to have arms as a bulwark against oppression) as well as to federal ones.
Now I'm not sure that private arms — or at least private arms at the level that we're likely to tolerate, which is to say some privately owned infantry weapons but without privately owned warplanes, heavy armor, anti-aircraft weapons, and the like — are likely to do much to deter or fight government tyranny in America today. It's possible that they would have this effect, especially against relatively mild-mannered opppressors; but I certainly can't muster the confidence for this that Madison or others expressed. (UPDATE: See also my colleague Stephen Bainbridge's post; he's even more skeptical than I am on this.)
But it does seem pretty clear that the "private gun ownership as check on government tyranny" view was quite prevalent in the Framing era, and was closely tied to the right to keep and bear arms. If holding such a view today makes the holders "gun nuts," then James Madison was a gun nut, too.