What they have in the store depends a great deal on who is running the section, and how much they sell. I am fortunate that the WalMart closest to me has a "gun guy" running the sporting goods, a collector and shooter himself. He always has plenty in stock, unless something happens and they short him on shipment.
I was in there a couple of days ago, getting my usual 9mm WWB and asked about .45 since I didn't see any at all. He said it didn't arrive with the rest of the shipment, so he had increased his order to 20,000 rounds and he would have plenty next week. I asked about 9mm quantities and he told me he generally gets 25,000 rounds of the 9mm at a time and always likes to have at least 2,000 rounds in stock. He sells me whole cases, but the manager won't let him discount it any more. They usually have a good assortment in the case and the rest is kept in the back.
I don't know about your store but I think if I asked him to stock ammo they didn't have he would probably start ordering it. He will order any shotgun or rifle, the WalMart website lists everything that is available, which is a much bigger selection that what they normally stock in any of the stores.
They just remodeled and took out the two round gun cases and put in a long case on the wall. Apparently guns and ammo move pretty quickly in that store, so they are going to stay.