‘Assault rifle’ is a very specific thing, and one whose costs put them well out of reach of most Americans. ‘Assault weapon’ on the other hand is a nebulous concept that means whatever a politician wants it to mean.
As a Ute, I was the proud owner of an Iver-Johnson semi-auto .22, ($19.95) complete with Birch stock, that was awesomely capable of spraying 15 or so shots within a three foot circle at 50 yards as fast as my grubby little trigger finger could squeeze the trigger and the other fingers wiped the continual spray of Three-in-One from my eyes. (Of course, I still have it!)
Nowadays, that same rifle would be tricked out with an AR-15 look-alike plastic stock, a pistol grip, a Picatinny Rail, a laser sight and scope, probably even a bi-pod, and maybe a curving magazine, instead of that rusty tube thing.
Voilà! An Assault Weapon!
There it is !!!