It's become almost an axiom that when choosing firearms you should always try to acquire the more common calibers on the theory that these will be the easiest to find ammo for during and after a major disaster. I myself have repeated this on more than one occasion. But I find myself questioning it now, at least a little.
Imagine this scenario: a small asteroid (>100 meters) is projected to strike the earth within 48 hours. You are near to, but not in the projected blast zone. However, the authorities expect hundreds of thousands of evacuees to shortly pour into your area. You decide that you better have another hundred rounds for your favorite hunting rifle. You scurry down to the local Walmart and get in line at the Sporting goods counter, only to find that the first 20 people ahead of you have bought out all of the 30.06 ammo. You are out of luck. But the guy behind you gets the 3 boxes of .280 Remington he needs because nobody else in line has a rifle in that caliber.
Some will argue that this is a good reason to stockpile. I'm not going to dispute that here. But it's just as easy to stockpile uncommon calibers as the common ones.
Others may argue that the reason to acquire the more common calibers is that it will be easier to find them after TSHTF. I can't argue with that either, but it seems to me that if you are worried about having to rely on others to supply you with ammo you might be better off increasing your own stash beforehand.
I guess maybe what I am trying to say is that the warning to stay away from uncommon calibers might be a little overblown. Comments anyone?