HT: That's another argument which the initial poster never mentioned when he said they were illegal to own.......
I was aware that being in possession of a firearm from which the original factory serial number had been removed was often illegal; however, many gun owners may not know that. (Unfortunately, our gun laws are about as complicated as our income tax laws, so it's exceptionally easy for Americans to unintentionally violate both sets of requirements & restrictions.) Another Freeper mentioned it in Posts #32 & #41:
18 U.S.C. 922(k):
(k) It shall be unlawful for any person knowingly to... possess or receive any firearm which has had the importer’s or manufacturer’s serial number removed, obliterated, or altered and has, at any time, been shipped or transported in interstate or foreign commerce.
I learned about gun laws almost 70 years ago when my father modified a .22 bolt-action single-shot for my small frame.