Trying to cut to the chase; there are two possible reasons that I can see, why a rogue government (and let’s be honest– that’s what we’ve had for some time now) would want to limit ammunition capacity. One would be simply to irritate and harass their political opposition, putting a few innocent people in jail now and then as a bonus. The other would be to limit the ability of the citizenry to fight against mass attacks (two or more assailants).i.e. to promote the ease of government attacking citizens. A possible third reason, going along in part with the first, would be to generally degrade society with more complex laws, more bureaucracy and more violent crime (criminals will have 30 round mags, but law-abiders won’t).
Any or all of those motivations would appeal naturally to any authoritarian, and to anyone who sees the founding of the U.S. as a problem (unfair, unjust, etc.)
If anyone can think of another reason, I’d like to know it.
ETA, 1-18-13; I’d thought of another, hoping maybe someone would chime in with it, and Publius pretty much, sort of did in comments here, though it’s not the way I would have put it. That motivation being to control the framework of the conflict (between liberty and authoritarianism), to keep us fighting THEIR fight and not ours. On that they have done a most excellent job– I bet you can find a million words, just today, about details of this or that proposed restriction and how it will not “work”. Well, it is working– they’re keeping us talking about THEIR ideas. As I’ve said before and elsewhere; it is a subtle yet crucial tactic, though most every little kid understands it. You see that bratty kid fussing loudly at his mother in the supermarket? He knows how to keep his mom off balance, off kilter, off her game, distracted, irritated, embarrassed, until he gets something from her (recently I noticed one such brat pause in his “tantrum” to look around and make sure he was getting a reaction from bystanders, then resume his fake tantrum, thus demonstrating that he understood exactly what he was doing). HE set the agenda, the framework of the conflict, not his mom. That one should have occurred to me foremost. It goes along with number one, but the distinction is between simply wanting to irritate your opposition on one hand, because you dislike them, and maintaining control of the whole discussion’s very framework on the other. The communists are experts at this.