Recently on Marilyn's discussion boards...
From robert 46:""Firearms require two precision-made chemicals: smokeless power and primers. Without them a firearm is nothing more than an expensive club.
OK then allow the guns - and ban the bullets."
By "bullets" I assume you mean "cartridges". Lead bullets are easy enough to cast, size and lubricate. Cases require either turning on a lathe or presswork. Smuggling ammunition should be no problem for accomplished current smugglers of everything from drugs to people.
3-D printers are a wonder. I envision a micro-chemical-factory which takes basic chemicals and fabricates a particular chemical structure as a development from nascient 3-D printing technology. There are already 3-D printers which fabricate parts in "steel", and one that builds a "house". There is amazing potential in the technology.