We have heard all sorts of theories ranging from dramatically increased military demand to a secret department of the government buying up all the primers on the market so they are unavailable to handloaders. None of those theories could be substantiated. In conversations with the major makers of primers and ammunition (ammunition availability shortages seem to begat primer shortages) it appears to be simple supply and demand, with demand reaching record levels and far exceeding supply and production capacity of both primers and ammunition.
Military demand is up with some makers, but not radically so when compared to 2007 and 2008. We have been told that availability of raw materials and powder delivery have affected production to some extent, but virtually every ammunition maker, large and small, is making as many cartridges as it can for sale to consumers. Production has been expanded everywhere possible, but conservatively. Major firms have been hesitant to purchase additional new tooling or add permanent employees out of uncertainty over future legislative issues from the current administration and Congress-and this is true of many firearm manufacturers with record backlogs as well.
One maker described demand for primers as "insatiable," and that firm reported record primer production already for 2009 but still can't keep up with demand. Primers are in extreme demand, and it's difficult if not impossible to quickly and radically increase primer production due to the nature of primer manufacture. Trust me, if you have ever seen primers being made, you don't want them to hurry.
In conversations with representatives from various mail order companies that specialize in ammunition, we were told that as soon as they unload a truck (not a box, but a truck), the ammunition is entered into their systems and is, literally, gone, often in mere hours. Ammunition is flowing steadily from makers through commercial channels, and it is being delivered to retail outlets. Some larger storefronts have ample supplies, but that can change in a matter of hours. [emphasis added]
Article here. Primers are one of the ammunition components that are difficult to improvise. You can usually get a hold of fired brass, cast your own bullets, probably even make your own black powder (not that I've tried), but I don't think there's really an alternative to commercially manufactured primers for the reloader. Is there?