1)Open your editor.
2)Press F1 if not defaulted.
3)Place an AAF MBT, player as commander
4)preview
5)switch to driver seat, find a decent hill to test it.(about 500m-600m far)(and high enough)
6)switch to the gunner, switch to coaxial gun.
7)Aim at a place, don't move your mouse,and start shooting.
8)starts from 100m zeroing up to 600, you will see it went just fine.
9)Since 600m, you will start to see bullet shift left a lot.
10)And when your zeroing reach 1800m, you will realize your bullet suddenly drop down to 100m zeroing, even it says "1800m";
11)Try 1800m-2400m, all the bullet drops till 100m point.