Please outline how you would go about changing policy and removing the approximately 400 million firearms in civilian hands within the US. Ignore any political

Please outline how you would go about changing policy and removing the approximately 400 million firearms in civilian hands within the US. Ignore any political complications like financial cost, or uncooperative media. There are people willing to go on murder sprees, and they number in the tens of thousands (or more) if anyone attempts this. Many of them are waiting, nearly holding their breath, hoping that the government tries such a thing. Quite possibly, a few of the mass shootings you've heard of were just those who "jumped the gun" (forgive the expression).