Would like verification form anyone experienced with JBM ballistic trajectory calculator. I just zeroed my AR15 at 25yds indoors. I want to adjust the elevation turret so that the rifle will be sighted at 100yds. According to JMB ballistic trajectory calculator when sighted at 25yds my 55gr bullets with a sight height of 2.8inches and traveling at 3000fps at the muzzle. will be 6.8inches high at 100yds. The calculator has a parameter called "zero height". Intuitively I know that the elevation turret must be lowered perhaps as much as 1 or 2 inches. So after several attempts I finally entered a negative 1.7inches in this space and recalculated which resulted in a 100yd zero. Did I use the JBM ballistic trajectory calculator correctly????