little late on this, just noticed it.

m855=xm855. The only difference between the two is that the xm855 didnt pass some sort of quality control check (usually something very minor), and rather than pay the fees to reinspect, they sell the whole lot off to one of 3 major companies, which then distributes them for civilian use. There is no difference otherwise. Same steel core and everything. Keep in mind these penetrators are designed for flak jackets, body armor, and light armor vehicles. If you're looking for something a bit more robust, you want to search out armor piercing rounds. You should be able to get them as a dealer through CDNN.