I think you'll find that the trucks making the deliveries arrive at different stores at different times. The stuff gets offloaded in the back somewhere and the sporting goods folks go pick it up on their own schedule. Some stores only have one person working in that department so they have to wait for a time when there's someone around to man the register.
In Ardmore, that truck gets there early in the morning and is unloaded by 7:00, or so. They go back to pick up their order sometime around 7:30 - 8:00. They pick up more than just ammo. If they hold the ammo until a later time, they'd have to stash it somewhere or they'd be pestered all day long. There's a lot of logistic crap involved just to satisfy guys like us.
You also have a inside guys , playing dirty!