Is this still the yanks buying up everything for the obamapocalypse, or what? Is production being curtailed. Import restrictions?
Civilian hoarding is to blame.
Many blame Obama but other than banning the import of the Korean surplus M1 Garands and carbines he hasn't done much of anything else to curtail firearms during his presidency. The vast majority of the time I see the name Obama used in internet forums it's just rumours and fear mongering that ends up causes more hoarding and panic buying. Mostly just conspiracy nuts talking about "secret executive orders" and "secret production limitations for manufacturers". I'm not saying Obama is a good president, I'm not a fan of him, but most of the accusations against him in terms of firearms policy are baseless.
Several of the ammunition companies have had their CEOs come out and say domestic, retail, civilian demand is what has caused the vast majority of the current shortages. Unprecedented demand from private citizens is to blame plain and simple. I believe Steve Hornady said in a video interview that military and law enforcement sales (FBI, NSA, Homeland Security, etc.) account for less than 10% of their sales.
There are no new US export restrictions, Canadian import restrictions, international sales restrictions, or any other new laws on the books in terms of powder, primers, bullets, or loaded ammo. Many manufacturers have switched to 24-hour production by adding extra shifts in order to try to meet demand. Several bullet manufacturers have temporarily discontinued certain less popular bullets to concentrate production on the top sellers (thus the current shortage of bullets for .303 British).