With a 70 pound weight limit, [USPS] Flat Rate [Priority Mail] boxes can be a fantastic deal, especially for small heavy items, as you mentioned. Up until this month, the two sizes available were 11″ x 8.5″ x 5.5″ and 13.625″ x 11.875″ x 3.375″. They cost $8.95 to send anywhere in the U.S.A. Now there is a third alternative, a larger 12” x 12” x 5-1/2” box that costs $12.95 to send (or $10.95 to an APO/FPO address). This is a real bargain.
I recently shipped a large quantity of these from Arizona to Alaska. Most of them contained quite heavy items, such as reloading lead, hand tools, and rocks. These boxes would have cost up to $50.00 each at regular parcel post rates.
The automatic handling equipment evidently knocks the boxes around. Heavy boxes get beat up a lot more than light boxes. If you ship a heavy box, it should be taped securely as you mentioned. It’s a good idea to tape all edges, and to wrap strapping tape around it in at least two directions.[JWR Adds: Be sure to cover any strapping tape with a couple of layers of opaque tape or Priority Mail tape, since strapping tape is discouraged by the USPS, for fear that it might gum up their automated parcel handling equipment.] You can ask the clerk to mark it “heavy” and sometimes they’ll run it through their strapping machine.
Incidentally, you can buy postage for Flat Rate Boxes online and just estimate the weight since you aren’t paying by weight anyway. Then you can have the carrier pick it up at your house. – K.L. – Alaska