Can someone please answer why we do battlesight zero this way? Below is text from the U.S. MARINE CORPS 25-METER ZEROING PROCEDURES from the M-16 manual. Why do you dial the rear sight all the way down then back up one click (to the Z) to zero in at 25yds? Why not just leave it all the way down? I followed these instructions and got my rifle hitting POA at 25 metres using the small aperture. When I switched to the large aperture and moved the elevation knob back to 6/3, my POI was low at 25 metres.
Greg
4 ROTATE ELEVATION KNOB IN THE DOWN DIRECTION (COUNTER-CLOCKWISE). THE ELEVATION KNOB SHOULD STOP THREE CLICKS PAST THE 300-METER MARK. THE REAR SIGHT SHOULD BE ALL THE WAY DOWN ON THE LAST WHOLE “CLICK†BEFORE IT BOTTOMS OUT. THIS IS CALLED MECHANICAL ZERO ELEVATION FOR THE REAR SIGHT. IF YOUR RANGE SCALE WILL NOT LINE UP IN THE ABOVE MANNER, AN ARMORER WILL BE REQUIRED TO ADJUST THE RANGE SCALE FOR YOU.
5 NOW ROTATE THE ELEVATION KNOB "UP" ONE CLICK PAST THE 300-METER MARK. FROM THIS POINT ON, THE REAR SIGHT ELEVATION KNOB SHOULD NOT BE MOVED. ANY CHANGES IN ELEVATION REQUIRED IN THE FOLLOWING ZEROING STEPS ARE MADE TO THE FRONT SIGHT POST ONLY.
Greg
4 ROTATE ELEVATION KNOB IN THE DOWN DIRECTION (COUNTER-CLOCKWISE). THE ELEVATION KNOB SHOULD STOP THREE CLICKS PAST THE 300-METER MARK. THE REAR SIGHT SHOULD BE ALL THE WAY DOWN ON THE LAST WHOLE “CLICK†BEFORE IT BOTTOMS OUT. THIS IS CALLED MECHANICAL ZERO ELEVATION FOR THE REAR SIGHT. IF YOUR RANGE SCALE WILL NOT LINE UP IN THE ABOVE MANNER, AN ARMORER WILL BE REQUIRED TO ADJUST THE RANGE SCALE FOR YOU.
5 NOW ROTATE THE ELEVATION KNOB "UP" ONE CLICK PAST THE 300-METER MARK. FROM THIS POINT ON, THE REAR SIGHT ELEVATION KNOB SHOULD NOT BE MOVED. ANY CHANGES IN ELEVATION REQUIRED IN THE FOLLOWING ZEROING STEPS ARE MADE TO THE FRONT SIGHT POST ONLY.