It's not hoarding, it's panic buying. People panic buy stuff because other people panic buy stuff and the empty shelves fuel the panic buying frenzy.
Hoarding is what you do between buying panics so you have ammo to tide you through a buying panic.
I predict that in a couple of years, the shelves will be full of .22 ammo again and then is the time to stock up, preferably when the stuff is on sale, so you'll have ammo to shoot during the next buying panic.
I remember an antifreeze buying panic back in the '70s, couldn't find any Prestone to put in my car anywhere. People were buying it by the case at scalper prices. I bet some of them still kick themselves every time they look at that pallet of antifreeze they paid premium prices for in their garage.
Once a buying panic starts, it takes on a life of its own, those that had no intention to hoard find themselves buying whenever they can because the shelves are empty and the feedback loop is closed. It's like a run on a bank or a selling panic on the stock market, it feeds on itself.