“All right, full auto!” he said as about half the spray of bullets ricocheted off the coffin-shaped target while the rest flew into the dirt behind it. He burst through the entire magazine in less than a second.

“I can’t believe how many rounds I burned through already,” Hickok45 said after ringing more steel, then exploding a terra cotta pot, popping several soda bottles and knocking over a bowling pin. “It’s fun. And we wanted to bring the fun to you.” The video has attracted 681,000 views.

Congress first tightened regulation of machine guns back in 1934, in response to Prohibition-era gang violence. Modern machine guns and conversion devices have been banned from civilian use since 1986. Unlawful possession of an autosear can land an offender in prison for up to a decade, whether or not the device is attached to a pistol.

But machine guns are making a fast comeback.

Tinkerers are constantly devising new ways to shoot semiautomatics faster. The 3D printer has made it possible to turn a common pistol into a machine gun for less than $100. And the spread of information in the digital age has made it easier for enthusiasts like Greg Kinman of Tennessee, who posts on social media as Hickok45, to jump through the hoops necessary to buy or build fully automatic weapons legally.

That rapidly growing market has created new challenges for law enforcement. The Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) is waging a public education campaign to help dispel the notion that machine gun conversion devices like the ones portrayed in Hickok45′s video are legal. Some Democratic-led jurisdictions are taking legal action against Glock in an attempt to make its guns harder to modify.

But lawmakers and regulators face a complex problem that piecemeal efforts are unlikely to solve. The result is that faster-shooting guns — both legal and illegal — are likely to become an increasingly common fact of modern American life.