Hey, i shoot a savage in .243 and i keep having problems getting JBM and an excel program called pejsa ballistics which is in excel to give me accurate predictions with the real weather conditions, and bullet speed and data. For example, i can get JBM to give me everything correctly with the real temp, humidity, and elevation, real bullet data, which is 6mm 105 Amax, and 100y zero which i use when shooting, but i have to insert 2960 ft/s at the muzzle and i chrono'ed this load at 2800. Now using pejsa ballistics with the same bullet info, REAL velocity of 2800, scope height set to 2.75 in when its really more like 1.75, i measured, and the temp set to 75 celsius which is WAY hot, i can get it to b about spot on. y is this? just a wierd occurence? something to expect from free ballistics calculators? Thanks for reading and any advice!