That explains his kill ratio being so noteworthy. With 30 victims, and 10 shots each (many might not have been shot 10 times, but he certainly didn’t hit with every shot either), that’s 300 rounds. With handguns, that’s likely about 30 clips.(Did he carry a backpack? 30 clips is not going to fit in a few pockets.) He had to reload many, many times. Too bad nobody rushed him during those moments.
He had a Bushmaster which appears to have been his primary weapon. They sell a 30 round magazine on the Internet. I don’t know if that is what he used though.
Magazines. Clips are used in revolvers and old garands.