[Findecanor]

How about blasting caps? Those are integrated into modern brass cartridges, and I think making them that way would require more precision than you'd be able to achieve with simple hand tools and an anvil.

19th century revolvers tended to require separate blasting caps, but you still had to buy them even if you could make the bullets.

[elictronic]

Tiny objects are harder to regulate. Many drugs are illegal but are still easily accessible due to their small size and transportability.

The correct action at this point in a society that wanted to keep guns legal but better regulated would be regulation of barrels. They are the only item left that are truly difficult to make in quantity and hide easily.

[parineum]

Shotguns don't need rifling.

[bigfatkitten]

Electronic firing is an option. It’s well proven on aircraft autocannons.