What's causing the shortage? Hoarding, or production cuts?
There are people out there who know when the delivery trucks show up at different stores and they will literally wait for the trucks, and grab it up as soon as it hits the shelf, some are just hoarding it, others are reselling it online or at gun shows for ridiculous prices (gouging). At one local retailer near here, they put out the ammo shipment every Wednesday when they open, and people start lining up hours before opening to get some.
As for production, it's the opposite of cuts. I know a man who is the owner of a large bullet, and ammunition maker. I talked to him last about a month ago, he tells me that his factory, (and every other manufacturer) are running at max capacity. They simply can't make any more ammo with the facilities they now have, and they are weary about tooling up to build new facilities for what may just be a bubble. However I am beginning to think that this may be the new norm, and if this type of demand keeps up long term, then most ammo makers will probably expand their production capabilities.
Bottom line is the ammo shortage is self-inflicted. If every stopped buying for a month, the supply line would catch back up and the shelves would be full... that ain't gonna happen though.
There is also another variable that I've heard few people talk about. That is new gun owners and shooters, with the current politics around guns many NEW have gotten into shooting as a kind of knee-jerk reaction.
So we have a combination of established and long time shooters hoarding, brand new shooters expanding the market size, and then the D-bags that are buying it up to resell at ridiculous prices to said new shooters who don't know any better.
It ain't just factory cartridges either, it's difficult to find some reloading supplies like primers and certain powders now as well.