Don't take me wrong, but the ability to compete in matches under current rules is laughably insignificant when talking about saving the lives of young children.
That's nothing I'd care to advance as an argument against the magazine-limit legislation. I would hang my hat on the original purpose of the 2nd Amendment being to promote marksmanship with military-type weapons, and the possession of "high-capacity" magazines giving citizens some degree of parity with soldiers of an invading nation, or our national government turned tyrannical.
Violence is an ugly thing, but not the ugliest of things. The decayed and degraded state of moral and valorous feeling which believes that nothing is worth violence is much worse. Those who have nothing for which they are willing to fight; nothing they care about more than their own personal safety; are miserable creatures who have no chance of being free, unless made and kept so by the exertions of those better than themselves. Gary L. Griffiths, Chief Instructor, Advanced Force Tactics, Inc. (Paraphrasing John Stuart Mill)