How is the battlesight zero for each caliber determined. Is a vital zone in inches used and then the data from the ballistics of the cartridge used to determine the yardage that bullet can stay within that zone? I know what is is for the 5.56 NATO, 7.62x51 NATO, 7.62x39, and others that are listed just about everywhere. What I need is for the 6.8. I'm basing this on a 90gr projectile with a muzzle velocity of 2900fps, and a ballistic coefficient of .275. Speer TNT as loaded by SSA in their combat load. I will probably just match that for my handloads, or just exceed it, but no more than another 100fps. There are other bullets coming on line now that will be in the 100gr range that have a much higher b.c., and I will most likely switch over, but right now I have 650 90gr TNTs to load up. Thanks