That's an interesting point, JimDandy.
I have to say that I find the magazine argument in general a particularly frustrating one. For every person who says, "A large magazine capacity offers little to no practical advantage," there's someone else who says, "But we need them because the bad guys have them." Sometimes it's the same person arguing both. I'm not sure that you can argue both. I think you have to choose.
In any case, this thread is more about ammunition sales.
Does anyone have any idea which mass killing entailed the largest number of shots being fired? I'm guessing Columbine, as there were two shooters. But I think Breivik in Norway, and Bryant in Australia, both got off a lot of rounds. In each case the shooting went on for quite a while. But I still figure it was in the hundreds, not the thousands.