I'll give a little insight in regards to finding ammo instock at Walmart. The larger Walmart stores get trucks 7 days a week. A few of the small stores in small rural towns might just get them 5-6 days a week. Ammo is trickling in on just about every truck. Friday night my store got 75 boxes of 5.56mm. There have been nights recently where we've received as many as 25 100ct boxes of Federal 9mm.
If you want to see if your local store is getting some in that night, use Walmart.com. They start unloading the trucks at 4pm and they will update the inventory just a little after 4pm. Walmart.com doesn't show every kind of ammo that stores stock, but it does show some of the higher demand stuff. If you check the site around 5pm and it shows in stock but showed out of stock earlier in the day, then they are getting some in that night. Might not be on the shelf at 5pm, but it is coming in that night. Some stores are stocking ammo as the truck is unloaded and it's on the shelf as early as 6pm. Other stores are stocking it through the overnight hours and have it on the shelf by 7am. Visiting with the sporting goods associates in your local store will get you info on how or when they are stocking the ammo that comes in that night. Using the site will help you figure out some of what is coming in that night.
There is a three box per customer per day limit. Stinks for some of us that walk in and see twenty boxes you want to buy, but it's keeping away the people buying a ton just to sell on GunBroker or in local gun shops. It's lasting hours on the shelves instead of minutes now. I'd sure like to be able to buy more than three boxes, but it has resulted in more people being able to buy three boxes than all but one person being able to buy zero boxes.
Hope this helped a little.