I don't mean to stoke the fires of hoarding, but this is a preview of our world when/if SHTF. I worked for Chrysler for many years, until our plant was axed in 2008, we had been running for years on "Just in Time" delivery/inventory mode.
Today, virtually every retailer, manufacturer etc. runs J.I.T. When avenues of distribution breakdown, product becomes unavailable quickly. If you do not have adequate supply, you will be left out in the lerch p.d.q.!
As for ammo, get what you can, when you can because it has a very long shelf life! Barring any disruption of avenues of distribution, resupply will continue, and eventually demand will be satisfied.
Until the next perceived threat!