I tried to do some research on what the "X in XM193 stands for. I had been told and read that this means military rejected. Federals techs said that the "X" is to denote the civilian ammo. It is Lake City whether it is White Box A,B,C,D or whatever letter they are using today. The last letter is for packaging. Black box American Eagle is made by Lake City. I was told this in two diferent return phone calls by two different techs. " XM193 is not rejected". It is mil spec Lake City M193 I am sure some will doubt this.