Some possibilities:
The government will require indoor and outdoor ranges to verify only legal ammo is used.
Hunters will have to show purchase records of legal, serial number ammo in order to obtain a hunting license.
Game wardens, state police and others will be authorized to make random ammo checks of hunters, farmers and others carrying weapons, drivers of cars carrying game, etc.
Authorities will probably authorize and pay gun shops and ranges to be collection points for non-serial number ammo.
There will be severe penalties for those in possession of non-serial number ammo. It will be considered a violation as severe as owning a machine gun.
They will require retail and wholesale sellers to provide records of past ammo purchases.
We will probably see media reports on the dangers of old ammunition, especially in large quantities. People will be encouraged to report "dangerous caches" of old, non-serial number ammo.
State law enforcement will be battering down doors and making high profile, front page, 6 o'clock news arrests of contraband ammo owners in order to condition the public to the "threat" of these lawbreakers.
Later on there will probably be an effort to pass laws limiting the amount of ammo that can be purchased at one time and the number of rounds you can have in your possession.
It will be considered a violation as severe as owning a machine gun.
Words have meaning. It is, as you probably know, not illegal to own a properly licensed machine gun.
Oh please, this will never happen and if they try it it will son be past history. I’ve seen pictures and heard about the stockpiles many of these gun owners have, they aren’t giving it up without compensation. They have thousands of dollars into it.
Lots of outdoor ranges have no personnel there to monitor anything.
That makes it legal for them to CLOSE those ranges, eh???