It's true that the shelves seem to clear in a hurry. My neighbor and I have been monitoring closely at a WM "superstore" a mile from my home. Seems that they get two deliveries daily, morning and early evening, and that the merchandise is put on the shelves immediately. Last Saturday my neighbor found no 9 mm ammo on Saturday, but on Sunday at 8 AM it was there.
For some reason, WM prices are the lowest around, and the Federal "Champion" brand seems to be the new low price brand. For about the past month, we have seen Winchester "white box" pistol ammo in stock (sporadically) at $11.47 a box, and for just the past few weeks the Federal is $9.47 (box 50). They have had it in .40 much more so than 9 mm, it seems that the 9 clears off the shelf faster.
And I have seen quite a few bulk packs (Remington, Winchester, and Federal) of .22 ammo there. For most of the year you could buy 100 round boxes of CCI, but the bulk boxes were rarely seen. Maybe half the time, there would be little or no .22 there at all. I have little personal evaluation of these brands (my 10-22 seems to shoot OK with all of them) but from rimfirecentral and the reviews at Midway, the Federal gets good response. In the past two weeks, it has been there on the shelf (with a cheaper Remington box - about $12.50 per 500).
I think that it is notable to see more stock at Walmart, and to see lower pricing at the same time. This Federal pistol ammo price is better than any online pricing in the past year or so. Cheaper than even the gun show prices.
Check your local WM frequently, and if you can strike up a conversation with a clerk, get some info about when they stock it. It could be that the recent improvement in supply is local or regional, but I believe there is more stock moving through their distribution. It is without a doubt true that it still clears off their shelf in a hurry, but there are more opportunities in Dallas, within the past few weeks.