The United States appears to be experiencing a rec­ord run on military-style assault weapons, high-capacity magazines and some kinds of ammunition as buyers deluge stores in search of guns and bullets they fear will be banned by the Obama administration, according to firearms industry executives and market analysts.

Even allowing for spikes in gun sales that follow every mass killing in the United States and attendant political debates about gun control, industry executives said the surge seems unprecedented.

And it has emptied shelves of the kind of semiautomatic rifle that was used to kill 20 children and six educators at Sandy Hook Elementary School in Newtown, Conn., last month, the deaths that sparked President Obama’s proposal for tougher gun laws.

In some areas, a buyer walking into a gun store now will have to wait up to a year to buy a military-style assault weapon. The prices of available semiautomatics have doubled as buyers bid up the dwindling supply, and stocks of Glock handguns are also low.

“I think there has been a pretty dramatic uptick in demand within one month,” said Nima Samadi, who follows the gun industry for IBISWorld, a market research firm. “Certain locations are even running out of certain guns, and suppliers can’t fulfill demand.”

President Obama proposed expansive gun-control policies aimed at curbing gun violence. The Obama administration can implement about half of the proposals, but the others — arguably some of the more critical initiatives — will require congressional approval.

Samadi noted that 2012 was already a banner year for the gun industry, with projected 8.2 percent growth over 2011 — just as 2008, another presidential election year, saw a significant increase in gun sales.

The health and financial muscle of the gun industry was dramatically evident at the massive SHOT (Shooting, Hunting, Outdoor Trade) show here, where an estimated 60,000 people gathered to see, handle and buy firearms and accessories displayed by more than 1,600 exhibitors over more than 12 miles of convention space.

“2012 was a year of unparalleled growth and success for the firearms industry and its law-abiding customers,” said Stephen L. Sanetti, president of the National Shooting Sports Foundation, headquartered in Newtown.

Sanetti said that more than 73 percent of retailers surveyed by the gun manufacturers’ trade group had increased sales over the previous year, and that first-time buyers have increased to more than 25 percent of all customers.

“By late in 2012, retail firearm background checks had experienced 20 consecutive months of growth,” Sanetti said, indicating that gun stores were selling more weapons.

In December, the number of FBI background checks on prospective gun buyers increased in every state over November and over December 2011. In Virginia, checks jumped from 52,416 in November to 77,487 in December; in Maryland, from 17,048 to 19,172.

Nationally, there were 2,783,765 background checks last month, an increase of 38 percent over November, according to FBI statistics. That is the single highest month since 1998, the year the FBI launched the program as a requirement of the Brady Handgun Violence Prevention Act. On Dec. 21, the FBI processed 177,170 background checks, a single-day record.

These figures provide only a partial window into gun sales because they do not represent the number of firearms sold. A single background check can cover the purchase of multiple weapons, and private sales and transactions at gun shows do not require a background check. There is no federal data on total gun purchases in the United States.

At the Blue Ridge Arsenal in Chantilly, the effects of the debate are visible. “My shelves are bare,” said store manager Donel Dover, who said that he has run out of some kinds of semiautomatic weapons, and that the supply of .223-caliber and 5.56mm ammunition has dried up. “Some distributors have told us it will be six or seven months before they fill orders and that’s only going to get worse.”

Industry executives said the popularity of military-style assault weapons, called modern sporting rifles by manufacturers, stems partly from the wars of the past 20 years. Demand surged among veterans of the 1991 Persian Gulf War. The Bushmaster, the weapon used in the Newtown shooting, is the civilian version of the M-16, first used in the Vietnam War. While military weapons are automatic, those for sale are semiautomatic.

One U.S. official cautioned that the industry’s rhetoric about gun sales can be self-serving. “If people think Twinkies are going out of business, they’re going to buy Twinkies,” said the official, who was not authorized to discuss the issue publicly.

The National Rifle Association described Obama’s proposals to reduce gun violence as an effort to ban tens of millions of guns.

“The main goal of the gun banners in Congress is not to make schools safer, but to ban your guns and abolish every last sacred right you have under the Second Amendment . . . until they reduce your freedom to ashes,” the NRA said in its latest alert.

Finn reported from Washington. Julie Tate in Washington contributed to this report.