The knurling around the match brass was for brass used in M-852. This was the Lake City GI match ammo which shot well and used the 168 SMK.The Hague Convention prohibits the use of HP ammo in combat, so these cartridges had (for a time) the knurling around the base to indicate that they were not combat authorized ammo. The knurling was eliminated after a time. The brass is very good although there persists a rumor that the brass will separate at the knurl. I have never experienced this in using this brass for reloading. It's excellent brass. Sept.20, 2012