Also, be aware of fouling effects and heating of the barrel and the effects on accuracy.
I'd also look at your ammunition too. Different rifles shoot different bullets/loads more accuarately than others. I have quite trying to figure out why, but there are more factors that you can imagine.
Take this procedure that I use for zeroing my hunting rifles.
shoot 3 rounds at 25 yards, Pause 1 minute after each shot. adjust scope to zero.
Wait until barrel isn't warm to touch. Shoot 3 more rounds, pausing 3 minutes in between shots (to allow for cooling).
If I am within 1 inch I move to 100 yards.
then basically the same scenario at 100 yards. 1 shot wait 3 min, etc etc.
Now if you want to change ammo (bullet weight) you almost have to start all over again.
but, there isn't really a reason to move out to 100 yards if you aren't driving tacks at 25-50 yards. Do that first.