1st plane vs 2nd plane scopes. Most scopes are 2nd focal plane scopes, and the reticle does not change as you zoom. This casues issues with BDC scopes. The yardage spots have to shift as you zoom the scope, your field of view is getting smaller and each dot represents fewer yards if they did not shift. Some BDC scopes state they are only accurate at a certain zoom power. A mil-dot scope works well, as do the ranging reticles on Leupold or similar scopes. A 1st plane BDC scope will remain constant in POI throughout the zoom range.
I have limited experience with Nikons, and no experience with their BDC scopes.