A line of cars stretched down Howard Street early Saturday morning as people arrived with firearms in their trunks to exchange for cash, no questions asked.

The gun buyback was organized by the violence prevention group United Playaz in conjunction with the San Francisco Police Department.

By noon, when the buyback ended, 280 firearms had been turned in — ranging from a bazooka to BB guns — and were heading to be disassembled, ground up and melted down by specialists at the Police Department. This more than doubled the number turned in last year and included 142 handguns, 80 rifles, 42 shotguns, seven assault rifles and other miscellaneous firearms.

“It’s like a drive-through,” Rudy Corpuz Jr., executive director of United Playaz, said outside the organization’s Howard Street headquarters. “Except people drop off guns for cash.”

The process was simple: People showed up in cars, on foot and even on bikes, carrying guns they didn’t want. Police officers took the weapons to a nearby table, where they were assessed, secured and ultimately taken to be destroyed.

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People who brought the guns in were given cash: $100 for a handgun and $200 for assault weapons. “People can bring any gun,” said Joe Calderon, a member of United Playaz. “We don’t care; we don’t ask questions.” The anonymity is important for people who have illegal firearms they want to get rid of.

United Playaz hosts one buyback a year; this is their sixth. This year, they’re trying something new: repurposing the wooden parts of the guns after they’re destroyed. Corpuz said the wood will be given to inmates at San Quentin State Prison, who will craft them into bracelets. Then they’ll be sold, and profits will go to financing future gun buybacks. Corpuz pointed to his own bracelet, a set of wooden beads. “This used to be a gun,” he said.

December is a strategic time for a buyback, Corpuz said, because people want extra money for holiday shopping.

The firearms came in all shapes and sizes. There was a bazooka, an AK-47, small handguns, long rifles and even a cannonball. Some were in pristine condition, while others had duct tape around the barrels or partially sawed-off handles. One rifle came wrapped in a tube sock; another came swaddled in a purple bath rug.

Reed Kennedy, who walked in with his three guns around 9 a.m., had long thought about selling them but felt that missed the point: He didn’t want them to exist anymore. “My views on gun ownership have changed in the past 15 years,” Kennedy said. “I no longer believe that people should own guns for personal use.”

He had considered destroying his guns but knew it was unsafe to do so himself. Then last week he walked past a Muni station and saw a poster advertising the buyback. He walked out happily after handing them over, knowing they would soon be destroyed. Plus, he now had $300.

“We might have to go back to the bank,” said Glen Holden, another organizer. Holden credited the extra outreach they’d done this year. Acting Mayor London Breed appeared at a news conference with Corpuz on Wednesday, which he said probably helped. Also, they had a new outreach strategy.

“We had 10 ex-cons go into five regions,” Holden said. Last year, youth representatives did outreach, but this year they felt it was important that the message come from people whose lives had been impacted by gun violence.

Funding for the buyback came from several donors, including seven medical marijuana dispensaries and the Mayor’s Office of Housing and Community Development.

Sophie Haigney is a San Francisco Chronicle staff writer. Email: sophie.haigney@sfchronicle.com Twitter: @SophieHaigney