You are perfectly able to own an automatic rifle manufactured before 1986.Owning nothing newer than a quarter-century old (most likely much older and significantly used), at about a 25x markup, and submitting to strict licensing & monitoring, IF you can find anything close to what you actually want amid dwindling supply in a market more akin to "great art" investment than home defense ... hardly "perfectly able".
As an upstanding citizen, who may be called up for military duty at any time (i.e.: draft), I have a right to buy/make an M4 of my own without legal harassment & undue cost.
well regulated
Read that enumerated right as: "considering that a nation needs a standing army to remain secure, the fact that such a standing army exists does not in any way justify limiting the right of individual citizens from owning and appropriately using all the terrible instruments of the soldier, including cannons and battleships." Think about that long and hard, from the Founding Fathers' point of view (they had just overthrown domination by the world's superpower and wanted to enumerate key rights of the individual), before responding.
I've used automatic rifles. The fearful power most people impute on them doesn't exist; they're overrated (useful, but overrated). And yes, individuals should be allowed to own hand grenades, precisely because it is nobody else's right to "allow" such ownership so long as nobody is unduly threatened thereby. The "right" to restrict ownership only comes from situations where innocents are at genuine demonstrable risk of harm, at which point it's just a matter of self-defense by those innocents and their delegates (gov't/police); machine-guns & grenades do not inherently cross that line, while (yes) nukes do.
All this tangential arguing about weapons comes back to the basic argument against the thread's premise: you do NOT have the right to take my money without my permission and give it blindly to everyone else. Doing so on the pretext of "give poor people money so they don't kill me" violates my right to keep what is mine (and use it as I see fit), which is backed by my consequential right to use whatever tools necessary to enforce that right. Leave me be, and I'll be quite charitable; take what's mine by threat of force, with no more justification than mob rule, and equal force in response is justified - not because of what's taken, but because of the threat.