People were crowded five deep at the tiny counter of a gun shop near Atlanta, where a pastor from Knoxville, Tenn., was among the customers who showed up in person after the store’s Web site halted sales because of low inventory. Emptying gun cases and bare shelves gave a picked-over feel to gun stores in many states. High-capacity magazines, which some state and federal officials want to ban or restrict, were selling briskly across the country: one Iowa dealer said that 30-round magazines were fetching five times what they sold for just weeks ago.

Gun dealers and buyers alike said that the rapid growth in gun sales — which began climbing significantly after President Obama’s re-election and soared after the Dec. 14 shooting at a school in Newtown, Conn., prompted him to call for new gun laws — shows little sign of abating…

“If I had 1,000 AR-15s I could sell them in a week,” said Jack Smith, an independent gun dealer in Des Moines, referring to the popular style of semiautomatic rifle that drew national attention after Adam Lanza used one to kill 20 children and 6 adults at a Newtown school. “When I close, they beat on the glass to be let in,” Mr. Smith said of his customers. “They’ll wave money at me.”

Mr. Smith said many people were stocking up on high-capacity magazines in anticipation that they might be banned. Two weeks ago, he said, a 30-round rifle magazine was $12, but it now fetches $60. Popular online retailers were out of many 20- and 30-round rifle magazines.