Bump stocks — the gun add-ons that can dramatically increase their rate of fire — are now officially illegal in the U.S., according to NPR:
"Anyone selling or owning bump stocks could face up to 10 years in federal prison and a fine of $250,000 for each violation."
Bump stocks came under scrutiny after the October 2017 massacre in Las Vegas, according to CNN:
The incident left 58 people dead and 850 injured:
A buyback program ran out of money, according to another CNN report:
And ATF's enforcement plan is limited, according to The Trace:
"The agency has no requirement that individuals report that they have destroyed or turned in their bump stocks."
Schematic of the Las Vegas shooting scene, via Wikipedia.