At Walmart, all the guns arrive via FedEx, and that's anytime between 9 and 11 generally, they have to be received and then put out. Evidently the manager or somebody knows what's coming though....
The ammo arrives on their regular trucks about midnight, but isn't put out until the sporting goods guy comes in at 7am.
Funny story regarding N. 27th location....
I was there a few weeks ago just after 3:30pm when a guy showed up looking for an AR. He asked the salesman if they'd gotten any AR's in, to which the salesman (who evidently didn't normally work in that dept) didn't know what he was talking about and was completely confused. Just a couple seconds later, the phone rang, it was another customer asking about a Colt AR-15 rifle, to which the salesman told him to hold on while he checked. He told the guy standing there to hang on, and he went into the back room, came out, and told the guy on the phone they'd gotten one in. Evidently the customer on the phone said he wanted it and he'd be there in 10 minutes and the salesman said he'd hold it for him. Well, the customer standing there said "oh, if you've got an AR in I'll take it", to which the salesman replied that it was on hold for someone else now. Obviously the guy standing there was pissed, and argued first come, first serve, and he's got the cash right now. About that time the manager showed up, and asked the cashier what was going on, who was he holding it for, and explained to the guy standing there that he'd talked to this guy on the phone, in person at 6am, getting confirmation it was to arrive that day. Walmart ended up selling it to the 1st guy (on the phone) as promised.