Six features of an 1994 "Assault weapon":
Detachable magazine plus two or more of the following features-
pistol grip
bayonet mount
flash hider (but not compensator)
folding or extending butt stock
grenade launcher or barrel shroud (cant remember which at the moment)
Colt was also doing the "big front pin receiver" and filled Rdias area and ar15 vs m16 f/a machined bolt bullshit as they didn't like doing civilian sales at the time either. Other fun crap at the time was a "machine gun in a bag or envelope" where just having a shoe string with a ring for recoil impulse bump fired M1A was a ruled a "go to jail" offense by the courts. Just having some parts of an M16 in an AR was verboten (bolt carrier, various trigger parts regardless of weather or not it was capable of f/a) but you could literally buy just about every component off the shelf except the RDIAS itself, and I saw several of those for sale as well--legality unknown at the time, probably bogus as the MG registry was closed in 1986.
Bushmaster was selling lowers at that time, but several local FFL's didn't want to sell bare lowers because of ubiquitous "legal reasons" that they would never explain. Remember going to Dragon Man's to get a Bushy lower at the low low price of $150 and I thought it was a good deal at the time. Prices were through the roof and magazines started at a dollar per round of capacity and several were double that, even for the crappy clones that didn't work for shit.