For the box contents put "Limited Quantity Ammunition." At least that has worked for me. There is a limit of 60 pounds, if I remember correctly, for ammunition and said ammunition can't be over 50 caliber unless it's shotgun ammunition. The details are on the UPS site though it's not as easy to find as it should be.
You cannot take it to a UPS Store but you can take it to a main shipping center. Considering the price of gas and the distance to a shipping center in my area, I've found it more cost effective to have the box picked up at my home. The buyer should be paying for shipping anyway.
The black and white symbol is supposed to be attached point on point on the label side and must measure pretty close to a minimum of 4 inches. I attach mine first with glue and then with tape.
Measure and weigh your box, enter the details on the UPS site, pay and print your shipping label.
