The novel coronavirus is expected to put the U.S. economy into a deep freeze, but it's heating up an industry that was struggling just a few months ago: guns.

Kurt Green, manager of Staudt's Gun Shop in Harrisburg, Pennsylvania, said his store did $30,000 in sales on Monday alone. "It was easily the busiest day we've ever had," said Green, who added that sales at the nine-year-old store were up at least 50% from a typical day. Ammunition purchases also jumped more than 20%.

"When the economy goes bad, gun sales go good," Green said.

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Gun dealers around the country said they are seeing record numbers of customers in recent days. Online stores are having trouble keeping up. A message on the 1-800 order number for Ammo.com said "unusually high volume" meant "wait times will be longer than usual."

And gun buyers appear to be bucking recommendations by public health officials to avoid non-essential trips and crowds. On Tuesday, Adventure Outdoors had about 300 customers in its store, according to owner and manager Eric Wallace. The store, located in Smyrna, Georgia, is 80,000 square feet and advertises itself as the nation's largest gun store.

Wallace said Adventure Outdoors sold 500 guns on Monday. The biggest sellers where shotguns, AR-15 semi-automatic rifles and 9mm handguns. The store also recently sold out of freeze-dried food, while five-gallon water jugs are also selling quickly. Overall, sales are up about 400% so far this year.

Wallace said his store was selling relatively few hunting rifles. The main reason customers told him they were buying firearms — protection. "If martial law was declared, they want to be prepared to protect their homes," he said. "With this coronavirus, there is a fear of the unknown."

Some viral text messages circulating on Monday falsely claimed that President Donald Trump was close to ordering a total lockdown of the U.S. and a suspension of normal laws. Those messages have been widely debunked. On Monday, Republican Senator Marco Rubio of Florida implored Americans to "please stop spreading stupid rumors about marshall [sic] law," tweeting the rumors were "COMPLETELY FALSE."

Please stop spreading stupid rumors about marshall law. COMPLETELY FALSE We will continue to see closings & restrictions on hours of non-essential businesses in certain cities & states. But that is NOT marshall law. — Marco Rubio (@marcorubio) March 16, 2020

The pandemic is preventing some gun stores from capitalizing on the spike in demand for firearms. A message on the website of Poppie's Gun & Pawn in Salisbury, North Carolina, said the store had decided to close on Monday to comply with public health recommendations to slow the spread of the coronavirus. Other gun shops around the country were not answering their phones.

Until recently, firearm sales had tumbled in the past few years, in part because of reduced concerns about stricter gun regulation under President Donald Trump. A rash of mass shootings around the country also has driven some large companies and retailers to stop doing business with the gun industry. Walmart in September said it would end nearly all ammo sales after a mass shooting in its El Paso, Texas, store left 22 dead.

Shares of American Outdoor Brands, the maker of Smith & Wesson guns, had fallen from a high of $30 in 2016 to just under $6 late last year. On Monday, Wall Street had its second biggest drop in history, falling 12%. But the company's shares rose, capping a five-day jump of more than 50% to $8.50.

Another publicly traded gun manufacturer, Sturm, Ruger & Co., saw its stock price fall nearly 12% last year, but the shares are up by nearly the same amount this week.