A Walmart store in Walpole, Mass. The retailer has asked its customers to refrain from openly carrying firearms at its stores. (Steven Senne/AP)

Chad Howard carries a pistol everywhere he goes. And he isn’t about to stop now.

On Friday morning, he left home like he always does: with his .40-caliber Smith & Wesson pistol clipped to his right hip. He took his wife to the hospital for blood tests, then went to the local Walmart Supercenter in Corinth, Miss., where he waited to see whether he — and his visible firearm — would still be welcome.

Days earlier, Walmart had become the latest big-box chain to take a public stand on guns when it announced it would no longer allow customers to openly carry firearms in its 4,750 U.S. stores. The retailer said it would also stop selling ammunition for assault-style rifles and handguns, and would push Congress to pass tighter gun-control laws.

Walmart’s stand represented a major shift in the way retailers are positioning themselves in an increasingly fraught debate over who has the right to have guns, and where. And Walmart wasn’t alone. Within hours, Kroger, the country’s largest grocery chain, said it too would stop allowing customers to openly carry firearms at all 2,800 of its stores.

CVS, Walgreens and Wegmans made similar announcements in quick succession. In total, those retailers have more than 23,000 stores in the United States, though some of them are in places that already ban openly carrying guns. Other big chains, such as Target, Starbucks and Chipotle, have prohibited open-carry for years.

Gun-control advocates and industry experts hailed it as an admission by one of the country’s largest corporations that the government wasn’t doing enough to stop gun violence.

“The sheer size and power of Walmart means this is perhaps the biggest blow to the NRA in the history of the organization,” said Chris Allieri, a crisis management expert and founder of Mulberry & Astor, a public relations firm in New York. “This is not some left-leaning coastal CEO sending a tweet or two. This is Walmart saying. ‘This is how we’re going to do business going forward. Take note.’ ”

Although Americans took to social media to say Walmart’s efforts made them feel safer about shopping at the company’s stores, the National Rifle Association and gun rights groups increasingly are encouraging members to stop shopping at retailers that have tightened their open carry policies in recent days. Freedom Movement USA, a group of constitutional conservatives calling on a Walmart boycott, has had 3.5 million visitors on its Facebook pages since Tuesday, according to the group’s head, Brandon Harris.

Howard, 57, who calls himself “a constitutionalist and a Christian,” said the policy changes felt personal. He owns about 20 guns and has been openly carrying a pistol for six years. His wife keeps a revolver in the middle pocket of her purse. He said he quit going to Dick’s Sporting Goods last year after the company stopped selling assault-style rifles. Now he’s prepared to boycott Walmart too, if anyone there gives him trouble about his gun.

“With this world being the way it is, we’ve got to protect ourselves,” said Howard, who worked as a construction supervisor until he broke his back on the job 15 years ago. “I haven’t had to shoot anybody yet, but you never know. I’ve keep a fire extinguisher in my house even though I’ve never had to use it.”

On Friday morning, he strolled in like he always does. In the hour he spent buying groceries, he says he saw at least seven others — mostly white men like him in their 50s and 60s — who also had guns visibly strapped to their hips. He chatted with the manager and bought 2½ cases of shotgun shells.

When Howard’s experience was brought to Walmart’s attention, a spokesman said Friday that the company was working to add new signs and employee training that reflect its new open-carry policy in the coming months. In his statement Tuesday, chief executive Doug McMillon, who is also a gun owner, said the company will have “a very non-confrontational approach” to enforcing its new rules. It “will treat law-abiding customers with respect.”

Tom Gresham, the host of “Gun Talk,” a nationally syndicated radio show, says he will personally stop shopping at Walmart and that many of his listeners have told him they’ll do the same.

“The gun owners of America are not fooled,” he said. “Walmart has staked out its position in the culture wars, and we, the 100 million gun owners who don’t commit crimes, are like, wait a minute, you just threw us under the bus.”

Gresham, who has been carrying a concealed weapon for more than 25 years, says he hardly sees anybody openly carrying weapons near New Orleans, where he lives. “I probably have seen one person open-carrying this year,” he said. “But I know thousands of people who conceal-carry every day.”

Walmart’s new policy prohibiting open-carry, he says, doesn’t affect him. But the way he sees it, “these companies are doing nothing other than trying to show that they’re one of the cool kids.”

And although he’s carried around a firearm for at least 25 years, Gresham says it’s not something he likes to advertise.

“Getting away and being a good witness is often the best course of action,” he said. “If nobody knows I’m carrying a gun, it gives me an opportunity to do that.”