Howdy, Mandabear.
In my view, the 2nd amendment is some of the way down a chain of reasoning, not the beginning of it.
This chain, incidentally, answers a lot of other questions along the way, such as "who owns me, my work products, what are rights, and where doesn't government get any power to begin with?"
The 2nd amendment is all inextricably bound up in all that, and it's really hard to get all the nuances worked into a few pithy paragraphs.
--==|==--
My chain starts all the way at Taking Notice of my own Existence.
I exist.
I find inherent in my existence, (and as some would assert, "endowed of my creator") the absolute right to my own life, liberty, and justly acquired property.
No one has ever brought forth any argument that held water to the contrary, asserting that any other person or group had a higher claim on these things than me.
No one and nothing has any just right to interfere in this, and this forms the boundary and limitation of my own liberty, that I have no right to interfere in anyone else's, except in the defense of that which is rightly mine.
The 2A branch of the argument basically states that I have the right to any and all means and tools for such purpose.
Carrying on with the main thrust of the argument, if no individual has a just right to interfere with my prerogatives, there is no reason or justification that any collection of individuals, by virtue of their assembly, (or any other reason) has any claim either.
Now, as to government: The powers of government are formed of the delegation of my own just powers, and only for the just purposes of assisting me in the preservation of my own prerogatives. Government has no powers not granted to it, nor may I grant powers unto it which are not justly mine to begin with. For example, since I have no just power to enslave, I cannot grant that power to government, and any claim I make, a government makes, or any group of people make to the contrary is inherently fraudulent. (Not to mention evil.)
That's the *very* short course in the matter.
In general, the more some philosophical justification for a power varies from this, the greater your suspicion of it should be.
Check your own premises! What are your axioms? What magic does government posses?
Would you tolerate someone taking your tree cutting tools from you, because they baselessy feared you might go all axe murdery on them? And if one person hasn't the right, then why should some group have the right, just because they said they did? How is that any different from "might makes right"?