@8c08929b @394b5c0e for my hunting rifles I’m one of these guys, all the way back to 400m for initial and then on a new lot of ammo. 
For a 223/5.56 round 100 is fine, effective range is 300m but most people I see shoot don’t run glass to get that far much less reach out to 600m. 

 @9e8435e3 @394b5c0e for many AR15 pattern rifles, the ideal zero is 50/200m or 35/300.