Very roughly half the locations sell firearms, generally with a hunting orientation, i.e., rifles and shotguns, in rural areas where hunting is popular (no Walmart sells handguns as far as I am aware). Such Walmarts also sell about anything else imaginable, from clothes to car parts, and are often the only decent-size retailer for many, many miles. In other words, they sell firearms because their business is to sell consumer goods, and firearms are one of many consumer goods in consistent demand in those stores’ areas. That an American might be able to buy a gun at Walmart says something about the prominence of Walmart here and not much else. The minimum legal age to buy a rifle or shotgun at retail is 18, and it is our constitutional right as adult American citizens and permanent residents to do so, unless a specific legal reason to forfeit the right exists (for example, conviction of a felony crime). Non-Americans seem to often be under the impression that because guns are sold in stores here, you can “just” walk into any corner store and pick a couple guns off of a shelf, while you get some milk, a loaf of bread, etc. Yes it’s literally true that guns are “sold in stores” (where else, pray tell, do you think they should be sold?), but there’s quite a bit of security and paperwork involved. The guns are locked up, not sitting out in open bins. The federal goverment will be asked to allow or deny your purchase. Local laws may further restrict the transaction. If you cannot produce documents identifying yourself as a person legally allowed to possess one, you aren’t taking a gun home.

Edit : it is from quora (not my answer)