The tables of Sure Fire Florida, which background-checks buyers, were swamped.

A clerk said they quickly sold 40 AR-15s for as much as $2,800 shortly after opening. Some people had to wait two hours until their paperwork cleared before taking their guns home.

At a nearby booth, one seller soon ran out of hundreds of “bump-fire” trigger kits that, as a video showed, convert a semi-automatic weapon into a full machine gun that can fire 800 rounds a minute.

With numbers like that, it's safe to say more firearms were bought in the first few hours of the Miami gun show than were returned at an unrelated Miami police gun buy-back program that netted about 130 firearms Saturday and violence-plagued Liberty City.

“I’ve never seen it this busy,” said Naim Alherimi, in his fourth year at the Miami gun show. “Some people are talking about civil war and arming themselves like its World War III.”

But many have been heavily arming themselves and others and worrying about Obama long before a madman shot the school children of Sandy Hook with an AR-15.

In 2010, Florida gun shows were a major stage for Operation Castaway, “the most significant firearms trafficking investigation in Central Florida history,” according to the Bureau of Alcohol Tobacco, Firearms and Explosives.

The key player: Hugh Crumpler, a Vietnam vet turned small arms dealer who sold weapons to alleged affiliates of drug cartels and gangs in South and Central America, primarily Honduras, one of the most-violent countries in the world.

Crumpler was identified only because he was buying multiple handguns from federally licensed firearms dealers, primarily in his home of Brevard County. The handgun transactions were reported to ATF.

Had Crumpler only bought less-regulated (and more-powerful) semi-automatic rifles, no report would have been sent to ATF, which might not have jumped on his trail.

Crumpler sold at least 1,000 guns at shows from Tampa to Miami. He should have been a licensed firearms dealer because he sold so many weapons.

If a person isn’t a licensed firearms dealer and is technically a small-time private seller, he doesn’t have to do background checks on buyers.

“All my business is cash and carry,” Crumpler, working a booth at the Southern Classic Gun and Knife Show in Orlando, told an undercover ATF agent at the beginning of the investigation.

Asked if he background checked buyers, Crumpler said: “No. Obama won’t know that you have it.”

At another point, Crumpler explained his no-paperwork business model to an undercover agent.

“Most people are afraid that Obama is going to come take their guns away. Now whether he is or isn’t is not important. It’s just important that he might,” he said. “So they don’t want anybody to know. So I don’t keep a record. And if somebody comes and asks where the gun is at, I say I don’t remember.”

Crumpler’s quotes come from a plea deal he signed after becoming an informant. Later, Crumpler tried to appeal his sentence.

Crumpler compared his case to the botched Operation Fast and Furious, in which ATF agents in Arizona allowed guns to cross into Mexico to help track them.

Crumpler claimed Fast and Furious and Operation Castaway were ways for Obama to try to justify more gun control. The federal government denied it.