Strong believer in the Marine Corp shooting skills and methods. They use a 36 yard battle zero for their Aimpoint Comp M4 red dots. Your upward trajectory crosses zero at 36 yards. The downward trajectory crosses zero again around 260yds. The effective point blank range of never more than 4” above or 4” below the aiming point is out to 300yards. Don’t know about you, but that feels pretty good for no magnification. The math for zeroing 36 yards at 10 yards is 1 7/8” provided there is a 2.6” sight over bore. Using a white copier page and a straight edge draw parallel lines 1 7/8” apart. Mark an aiming point on the upper line. A cross or trace a penny. Put your dot on that when firing and your round should impact on the lower line. I was on a concrete slab with a table and bench using a bipod freefloated. Pretty solid and taking out as by human error and wind as possible. Was straight and on the 1 7/8” line in three shots. Take the next shot at an unknown distance somewhere over 100yards and hit it. The. Go to unknown target above 250 yards and hit level a foot off for wind and number two is on. Next four at the 1 7/8” lines for perfect wind age and elevation. Ten rounds and I’m good for a battle zero. The next mag at various random distance targets, using the trajectory of 4” high at 160yards to adjust for small misses on small targets. Basically the high point is half way to the 4” low point, proved the effectiveness.