Reloading time does not affect lethiality. Here's a video that shows how quickly one can reload with practice. I can manage it in about two or three seconds, and I haven't been to the range in forever.
http://www.democraticunderground.com/?com=view_post&forum=1002&pid=1020598
You may find the entire sub thread informative.
An alert on a hundred round purchase? For most shooters, a day at the range is two or three times that. For avid and competitive shooters it's a factor of ten. A one hundred round red flag would produce an ocean of useless data for preventing crime. And that's not to mention how easy it is to load your own. Although it would be a nice data mining opportunity for someone like Dick Cheney.
A lot of people don't know a lot about guns. And that's fine. But that lack of knowledge makes them susceptible to polls like these that snooker them into thinking workable policy is being discussed. And those polls get trotted out by people and used as a fallacious argumentum ad populum for their own ideological ends.
How many average Americans would have approved of deregulating the home lending market in 2006?