Forum Discussion
First of all, this is a wrong place. AHQ can't answer this kind of question, because we aren't game developers.
Secondly, now zeroing is set at 100m because of headglitch fix. Previously bullet was fired from a point which was head-high. After the Spring Patch it's fired torso-high. With 0m zeroing the bullet would go quite a bit below the line of aim regardless of distance. That's why the lower point from where the shot is fired is compensated by zeroing the rifle on 100m. According to calculations made by people from CTE the bullet won't go more than 4cm over the target you fire at when it is less than 100m away from you (and, from my experience, they're correct).
Long story short: 100m zeroing barely changes anything when it comes to aiming within 0-100m range as long as you don't aim at the very top part of the head.