An “assault rifle” is a term used for military rifles that may or may not have the features listed above but also have a selective fire capability that would make them machine guns under federal law.
BTW, a unmodified SKS at the moment is neither.
when i did this with my children, clintoon was president, the rifle had a lug for a bayonet...that was not illegal at the time, but actually attaching the bayonet made it an assault rifle