The XBP stands for Super X Black Powder, they were originally loaded as Black Powder blanks. I am sure they are standard Winchester 10ga hulls. Given the pressures involved I would feel quite confident and safe loading 19-21 grains of 700-x pushing 1 1/8 ounce of lead shot. I believe it's a load you will like. If you don't have one you want to get a hull skiver to open up and somewhat recondition the mouth of those hulls. Reloading hulls that were previously fired as a roll crimp can be a pain because it can be hard to get the wad started, the skiver helps to resolve this problem.
http://www.ballisticproducts.com/Pow...tinfo/0740011/