seriously dude? he wasn't shooting them from 100yds. Any gun would do the trick at classroom range. You can get a 30rd magazine for a glock too. Your argument doesn't hold up. I can also carry more 30rd glock magazines then AR magazines. Now what?
To prove your ignorance an AR magazine is 20-30 rounds also...
you know you can get 50 and 60 round magazines for the AR right?