"what is the purpose of a 30 round handgun mag?"
Most people are thinking of laws and government when they ask a question like that. What they are wondering is why it should not be illegal to own the mag, which is the same as asking "why should I not be allowed to use force to keep you from doing (X)." After all, the essence of government and laws is force.
When talking about the use of force/laws/government, I ask a different question: why SHOULD you be allowed to use force to restrain somebody from possessing/doing/saying something? I believe that force is only justified as a response to a threat to liberty. By "liberty," I mean unobstructed action according to one's will within the limits drawn by the equal right of others to do the same. The only legitimate purpose for laws or government or force is to protect liberty.
So when someone proposes to ban the mere possession of something, the question that should be asked is "how does the mere possession of this item constitute a threat to the liberty of others?"
It is difficult to come up with an explanation how the mere possession of ANYTHING can be considered a threat to anyone. I suppose the mere individual possession of something that has the capacity for extremely widespread destruction, such as a nuclear bomb, without any additional safeguards, could be considered a threat to one's life, liberty, or property by a rational person because of the possible magnitude of the damage of such a weapon.
Of course, if you accept this premise, this leads you into very subjective line-drawing territory... in the spectrum of dangerous weapons, where do you draw the line? When is something so powerful and destructive that it's mere possession can be considered a threat to the liberty of others?
When it comes to the protection of liberty, there is another issue: the fact that prohibiting the possession of weapons limits the ability of individuals to protect their own liberty against those who might violate it. Experience shows that the most serious violations of liberty usually come from the same people who claim the role of protecting everyone, along with the power to make laws and coerce people into following them.
So if the object is to provide for the maximum possible amount of liberty that can be equally shared, maybe one has to ask whether the mass destructiveness of a weapon outweighs it's usefulness in defending liberty and all other legitimate uses so greatly that it's mere unrestricted possession poses a threat to the liberty of others.
So maybe it is proper to ask what the possible defensive use of a weapon is. For any small arms, including the 30 round mag, it is an easy answer: the defensive use is to fight those who are attempting to deny liberty to you. Currently, small arms are the primary method humans use to kill each other, and are necessary to oppose an attempted use of force. This applies when the threatening party is a single individual or a small group (like criminals), but it's rationale is especially strong when the "threatenors" are organized and come in large numbers (like a government).
Recent conflicts have shown that small explosives are also highly effective for individuals resisting organized force, and I believe it is a violation of the liberty of individuals to keep them from owning such explosives.
Where the question becomes difficult for me is when it comes to weapons like anti-aircraft missiles and extremely large conventional explosives (like the one that destroyed the Murrah building). These weapons have some very powerful defensive uses... for situations in which one's oppressors are employing aircraft, or are grouped together in large numbers inside a structure for instance... but they also give the single individual who is intent on violating the right to live of his fellow man the ability to do so on a fairly large scale.
What do you think? Would a rational man perceive another person who possesses a nuke, or a Stinger missile, or a 2000 lb. laser guided bomb, or an RPG, or a Claymore mine, or a Glock with a 33 round mag, to be a threat to his liberty?
Personally, I do not believe that it is rational to see the mere possession of any kind of small arm to be a threat to anyone's liberty. I think this would be a good starting point... we should eliminate all restrictions on the ability of individuals to own small arms, and then we can worry about the other stuff.
