Its illegal but every new firearm is accounted for. When you buy a brand new pistol a round has been fired to A test the weapon and B keep a brass of what marking the firing pin does.
However, if your smart you just change the firing pin.

And no I dont know everything about guns. I know alot about guns, legal rules and whatnot. I own a "few" should we say. And currently I am doing all I can to buy as many semi autos as I can with all the democratic gun laws that are about to fuck us al l over.