Ammo shortage is much simpler than that.
- On a recent survey, firearms retailers reported 1 in 4 gun buyers were first-time buyers (reported a year or so ago). That is also an instant increase of ammo buyers, on top of previous existing demand.
- Existing non-hobbyist gun owners, who might have continued to buy a box or two as-needed, suddenly found empty shelves due to increased demand (election-related, more-buyers-related, whatever the reason). Once folks have been prevented from buying ammo one or more times, the NEXT time it's available, they buy more than they would otherwise need for one trip to the range, so they don't get shorted again. This is entirely rational; a gun without ammo is a paperweight or a club, at best. This is NOT hoarding! Think of it this way: no one buys gas for their vehicle based on what they think they will be needing for the next one or two quick uses of their vehicle. If you want to go shooting on your own schedule, not based on availability of ammo, you don't wait until you actually need ammo to buy it; you buy it when you can get it. So now, we have another increase in demand, driven by existing shooters/owners, and the longer this type of problem lasts, the more folks it affects (if you had a years' worth of rimfire ammo at the beginning of 2013, and haven't been able to buy more, you are now OUT, and you are now added to those folks searching for, and immediately buying, any ammo that they can find at a reasonable price).
- As the price for all types of ammo increased and the shortages became longer and/or more severe, some folks started to buy and "flip" ammo at increased prices to make money. Again, another increase in demand (these folks would not have been buying, or not buying at an increased rate, if the market hadn't gotten so short).
- As more folks found that centerfire ammo was in increasingly short supply (or at a much higher cost), they began to switch over to shooting rimfires whenever they could. This, combined with the new shooters who bought rimfire rifles/pistols for their first gun purchase (a long-time recommendation for non-defense-related gun buyers), created a spike in the demand for rimfire ammo that continues to this day.
Not rocket science, just supply and demand; greatly increased demand, and supply can't keep up. The manufacturers ramped-up production by adding extra shifts (verified by multiple sources), but WILL NOT add production capacity (more machines/plants) based on what they see as a temporary surge in orders. Again, totally rational.
"Placement is power" -- seen in an article by Stephen A. Camp
(RIP, Mr. Camp; you will be remembered, and missed)