But the reality is brutal. The ATF has long since closed the loophole of "it’s for my keys." The presence of a key ring does not magically un-design a machine gun part. Carrying one is like carrying an unregistered hand grenade with a lanyard attached: the lanyard doesn’t make it less dangerous, and the keychain doesn’t make it less illegal.
: Possession of an unregistered auto sear is a federal felony. It can result in up to 10 years in federal prison and significant fines. Sting Operations : Federal agencies like the US Postal Inspection Service Drop In Auto Sear Keychain