Considering how much ammo Walmart sells, they'd have to make a LOT of seconds.I had a gun shop tell me about the Walmart ammo is manufacturers seconds. I bought a box of his for $10.50 for a 50 round box (Federal) only to discover later that the Walmart is the same damn thing, Federal in the exact same box except it is a 100 round economy pack.
Walmart often sells its ammo retail for less than a LGS can buy it wholesale, but they get the low price by buying in trainloads instead of cases.