When does a firearm stop being a firearm?

[still afloat]

What % of change or stage of disassembly or steps to render a firearm unuseable would be required to remove a firearm from the definition of a firearm?
Such as if you shove a fan blade in the end of the barrel and call it a weather vein is it a weather vein or a firearm? Or run an electric cord through the barrel and put a lamp socket on the end is it a lamp or a firearm?
How would altering a firearm to a form of art or functional device such as the lamp affect the sale or transfer of the firearm?

[Dogman]

I think the gun has to be totally rendered useless so that it can not be used as a working gun again.

Or all the parts that make it function can not be together in the same area and the parts are scattered, ????

[madfranks]

If said firearm has no bullets in it, it is rendered useless and can't hurt anyone, except maybe as a club.

[Heimdhal]

The ATF states the receiever must be destroyed. This includes crushing it completley, melting it, beating it or cutting through it entirley (straight down, chop right through).

The only part of any gun that is a "gun", according to the ATF, is the receiver. That is what you 4473's out for, that is what is FFL transfered, etc etc.

Thats what the ATF says anyways....