Here is the NY Times describing a U Penn study on the efficacy of thre assault weapons ban:
The federal ban also yielded mixed results in its decade of existence. A 2004 study by the University of Pennsylvania, financed by the Justice Department, found that the measure, which included a ban on ammunition magazines that could hold more than 10 rounds, had only a limited impact on gun crime.
The study explained that part of the issue was all the exceptions to the law. Assault weapons and large-capacity magazines manufactured before 1994 were exempted from the ban, meaning that more than 1.5 million assault weapons remained in circulation. In addition, the country’s stock of large-capacity magazines actually continued to grow after the ban, because it remained legal to import them as long as they had been made before the ban.
Another challenge for lawmakers was defining precisely what an assault weapon is, which allowed the industry to continue manufacturing guns similar to those that had been banned.
Yes, finding a meaningful definition of "assault weapon" was surely a challenge. But the U Penn study also identified an even larger challenge:
AWs [Assault Weapons] were used in only a small fraction of gun crimes prior to the ban: about 2% according to most studies and no more than 8%. Most of the AWs used in crime are assault pistols rather than assault rifles.
Eugene Volokh had the way of it - this was an attempt to reduce drunk driving by banning the sale of whiskey. Imported Canadian whiskey.
U Penn does mention that Large Capacity Magazine (also referred to by the media cognoscenti as "high magazine clips") are somewhat more relevant:
LCMs are used in crime much more often than AWs and accounted for 14% to 26% of guns used in crime prior to the ban.
In response to which others have noted that the Va Tech killer (still the worst school shooting in the US) used ten and fifteen round clips; reloading can be very quick.
Well, tear out the front page of my blog - the Times coverage is woefully incomplete and slanted. You can only imagine my surprise.