For a new scope I follow much the same process as you.
First I hold the scope against a mirror and centre the crosshairs.
Next I mount the scope.
I then remove the bolt and do an eyeball bore sight at a distant object. When I get to the range I may confirm the bore sight against the 100.
I then zero it at 50 yards, then move to 100 and adjust accordingly.
Lastly I set the gun aside or come back the next day when the barrel is cold and do a SINGLE shot. I wait about 15 minutes doing other stuff and do another single shot. If need be I tweak my cold (and dirty) bore zero.
I never go back and repeat any of this. Instead I just try and get my rifle out a few times a year for target practice or ammo load development.
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