Only semi-correct, they had full-auto AK47s and extended mags, all of which at the time could be purchased and legally owned with a special stamp by the ATF [0]. As a child a friend's father had one he would bring out on new years to only short lived amusement in the neighborhood as we all lived in a densely populated suburb near a major freeway.
But without them, yes, you couldn't just go to a store and buy one off the shelf.
0: https://legalbeagle.com/8731203-class-three-stamp-through-at...
