I worked in management at Wal-Mart about 10 years ago, for several years. I was sporting goods manager for a year. The guns sold there come from the same suppliers that 99% of gun dealers use, Sports South and Lipsey's. Just like at Dick's, Bass Pro, etc, Wal-Mart will have special runs that are exclusively available there. For years, it was the ONLY store you could by Weatherby Vanguard rifles at.
As far as I am aware, no stores ever really carried handguns in stock. We had no display space allocated for them. We had to special order them upon customer request. I usually had a couple of hot sellers stored in the firearm stock room to show customers.
How good your local store's sporting goods department really is depends on the store management. If the store has a department manager or store manager that's an outdoors person, then the sporting goods area tends to be good. Each store has a departmental plan for their store that doesn't allow much flexibility, but a good manager can make it work.
Here's an example: The stores a couple of miles away from my house SUCK ASS in all ways. They don't have much of a selection at all. They are always out of stock on stuff they do carry. No offense to the females on here, but all three of those stores have women for the sporting goods manager. You can tell they aren't interested in the stuff at all, but they've got no other department to manage. Conversely, a store about 40 miles away is fabulous. The store manager is a hunter, and the guys working the sporting goods are all avid hunters and fisherman.
Everyone wants to hate on Wal-Mart, but the reason that they are how they are is because that's what customers want. Everyone wants stuff for the cheapest price possible. All they did was answer the demand.