Unfortunately the ammo makers can only make it so fast. When a panic buying frenzy hits they just can't keep up.
Think about this: They normally make millions and millions of .22 rounds per year. Let's say there are 50 million .22 rifles/handguns out there in the public domain. Now if, in an average year, one (1) 50 round box is purchased for each gun that would be 2,500,000,000 rounds per year (if my math is correct!).
Now, when you consider that a LOT of people who ordinarily would buy only one or two boxes or maybe a brick per year are stockpiling 50,000 rounds or more it's no mystery why it's so scarce right now!
The actions of the king and his court are what set off the panic buying spree, but it's the panic itself that makes the shortage.