maybe you do not have the scope sighted to 50 yds. the bullet is probabley crossing the line of sight at 50yds, continuing on it's up ward trajectory and will come down and cross it again at some distance (maybe 600).
try this.
put the rifle on sand bags. take out the bolt and line up the bore at a 25 yd bulls eye. now adjust the elevation so that it is lines up with the 25 yd bull.
fire a round at 200 yds, at a big target. staple two target one over the other.
You should be pretty close. (notice how many rounds you have fired at this point 1)
If things are still not working out you are going to have to shim the bases to get the calibration on the scope lined up with point of impact. If the scope is calibrated for 8x57 make sure you use the right load.
