The Ruger 10/22 rifle with a pistol grip and a folding stock was classified as an assault weapon under the Federal Assault Weapons Ban.

https://en.m.wikipedia.org/wiki/Assault_weapon

The AR 15s come in various configurations and are quite modular from what I gather.

Collapsible stocks and vertical front handles etc. Clearly originally made for use cases that differ from hunting animals.

They look cool though!