For more than a year, the Georgia Gun Store in Gainesville had no requests for a bump stock — an accessory that transforms a semi-automatic rifle into a weapon capable of firing hundreds of rounds a minute.

Key points: Bump stocks have been selling out at gun stores after the Las Vegas shooting

Bump stocks have been selling out at gun stores after the Las Vegas shooting Other online stores have pulled the item from sale

Other online stores have pulled the item from sale Some Republicans are considering banning the stocks

But following Sunday's mass shooting in Las Vegas, the shop fielded several calls from customers asking about the product.

The store's owner, Kellie Weeks, said several distributors were out of stock when she called them seeking supplies.

"Anybody that wants to get them is probably just worried that they're going to be banned," Ms Weeks said.

Authorities say the shooter, Stephen Paddock, had 12 rifles outfitted with bump stocks among the arsenal of weapons in his hotel room, and audio of the attack suggested he used weapons with rapid-fire capabilities.

Sorry, this video has expired Video shows chaos outside Las Vegas concert as shooting unfolds.

"They do sell a little bit, but it's very minimal," said CJ Calesa, an employee at Birmingham Pistol Wholesale in Trustville, Alabama.

"We usually sell 10 or so a year."

What is a bump stock? A bump stock basically replaces a gun's shoulder rest with a "support step" that covers the trigger opening. By holding the pistol grip with one hand and pushing forward on the barrel with the other, the shooter's finger comes in contact with the trigger. The recoil causes the gun to buck back and forth, "bumping" the trigger and firing rounds much faster than if the shooter were to manually pull the trigger each time. The stock effectively turns a semi-automatic weapon into a fully automatic one that can unleash continuous rounds until the magazines are empty with a single trigger pull.

Calesa said the store began receiving calls from customers about bump stocks on Tuesday.

Slide Fire, a leading bump stock manufacturer, has sold out.

Customers can sign up to be notified when more bump stocks become available.

"We have decided to temporarily suspend taking new orders in order to provide the best service with those already placed," the website reads.

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On Wednesday, comments on the Facebook page for Slide Fire were split between critics who blamed the company for the massacre and customers who said they planned to buy more bump stocks.

Several other online retailers also list the item as being out of stock.

Stocks in companies that make guns also rose sharply on news of the Las Vegas shooting

Some of America's biggest online stores have pulled the stocks

Shooting instructor Frankie McRae aims an AR-15 rifle fitted with a "bump stock" at his 37 PSR Gun Club. ( AP: Allen G. Breed )

One of America's biggest retailers, Walmart, pulled bump stocks from its website in the wake of the shooting.

In a statement provided to Business Insider, Walmart said the stocks were sold by a "third party retailer" and "never should have been sold on our site".

Cabela's, one of America's largest outdoor and sporting goods stores, did not respond to a Reuters request for comment.

Links to pages on Cabela's website which used to sell the stocks tell customers the items are "currently unavailable".

So could they actually be banned?

Some Republicans are warming to the idea.

The second most powerful Republican in the US House of Representatives said he expects Congress will take steps to control the use of bump stock gun accessories.

"This is definitely an area we should look at," House Majority Leader Kevin McCarthy told the Fox News.

"The one thing I do want to do is, let's let the sheriff and the authorities carry out their entire investigation," Mr McCarthy said.

"But I think this is definitely an area we're going to look [at] and be able to act on."

Senior Senate Republican from Texas John Cornyn also broke ranks with other Republicans and President Donald Trump, who have shied away from talking about gun control in the wake of the massacre.

"If somebody can essentially convert a semi-automatic weapon by buying one of these and utilising it and cause the kind of mayhem and mass casualties that we saw in Las Vegas, that's something of obvious concern that we ought to explore," Mr Cornyn told reporters.

"I own a lot of guns and as a hunter and sportsman I think that's our right as Americans, but I don't understand the use of this bump stock."

A bump stock is a device that attaches to a weapon to speed up fire. ( AP: Allen Breed (file) )

At least one Republican senator, Ron Johnson of Wisconsin, said outright he was prepared to vote to ban bump stocks.

"I have no problem in banning those," he said.

The US Government gave its seal of approval to selling the devices in 2010 after concluding that they did not violate federal law.

Retuers/ABC