I live in suburban Detroit as well and that is exactly what shopping at WalFarts is like. Went yesterday and left with a whopping 2 boxes of Federal 115 gr. Don't know about the rest of the country, but Walfarts here get stock on Wednesdays. By Thursday the ammo is gone. As far as what is the best bulk, whatever you can find that is less than 25 cents a round that shoots reliably in your guns.
A well regulated militia being necessary to the security of a free state, the right of the people to keep and bear arms shall not be infringed.
Molon Labe