Actually, the Clinton ban couldn't ban semi-autos, so it had to ban cosmetic features, such as bayonet lugs, flash hiders and pistol grips, so during the Clinton ban we bought these same guns only with thumbhole stocks, instead of these with pistol grip stocks, they shot exactly the same and we bought a lot of them, MILLIONS!
Also where the Chinese AK was banned by name, we got the Chinese MAK-90 same gun with a thumbhole stock, eat shit hippies.
UBC's won't stop black market sales, just like drug laws don't stop drugs.
Furthermore, without universal registration, UBC's would be that much harder to even try to enforce.
Registration is used later for confiscation, so you would never get even 25% compliance, some States have proven this out.