As others have said, nothing wrong with wal mart ammo. I do not believe that they do this with ammo, but I know there are some specific items that are made cheaper by companies just to fulfill Walmart's very large order. For example, widget X is sold at Walmart, Kohls, and dozens of other stores. Walmart order 200,000 units of widget X, but only wants to pay a price well below wholesale. The manufacturer of widget X wants that contract, but wants a profit margin more than 2%. A cheaper material/method of manufacture is created for the Wal Mart order. In other words, corners are cut. Sometimes this has no real effect on the quality of widget X... sometimes it does. This cheaper model usually is the norm for all retailers in the future, but stores that do less volume than Wal Mart may have the older (more expensive to make and maybe better quality) widget X in stock for quite some time.
And I am not a fan of some of Wal-Mart's practices either. I shop there, but I try to limit the money I give them. I prefer to go outside the "big box" retailers if I can help it.