I'm a little late to the party but I have a few notes to add...
There are labeling regulations as ammunition is ORM-D material.
First of all, the ORM-D label is being phased out and replaced by a "Limited Quantities" symbol. However, the ORM-D labels can still be used for a while. More info here:
http://parallaxscurioandrelicfirear...-D-Labels-for-Shipping-Ammo.html#.T3h3fHnh98E
Second, I once read in an online shipping policy guidebook (FedEx I think, but I can't find it...) that USDOT guidelines call for ORM-D shipments to be contained in corrugated cardboard boxes with a 200 psi edge-test rating. These are not too hard to find, but many consumer products and mail-order shipments come in lighter-duty boxes, so using a "recycled" box may not meet the standard. That said, this seems to be loosely enforced, if it's enforced at all.
Third- and more importantly- I would recommend going to company-staffed FedEx or UPS hub or requesting a driver pickup. I'm not sure if the strip-center UPS Store (which are privately-owned franchises) or FedEx Office locations are authorized to handle ammo; however, even if they technically are, I've found that the employees at these places are often ill-informed about company shipment policies and are skittish about handling anything remotely resembling HazMat.
If you really, really want to use on of these places, I recommend
at least calling ahead.
Fourth, in case you didn't already know this,
nobody can ship ammo via US Mail. This
includes FFL dealers, manufacturers, and pawnbrokers. They don't get a free pass like they do for handguns. (There have been past threads on this forum in which some people have gotten this mixed up.)