I sighted in a bunch of rifles over time. Being a hand loader I know the weight of my bullets and the speed they travel so I rely on the charts in my load manuals on the drop of the bullet.
220 swift 55gr. bullet goes 3800FPS so a sight in of 1.5 inches low at 100 yards with it makes it a dead hold out to 600 yards.
I start with a home made rest, take the bolt out of a bolt rifle and aim the bore to a target at 25 yards once that is done I line the cross hairs up on that target.
Once I am sure the scope is on target I shoot the rifle/slug gun to make sure.
Then depending on the game I am hunting and area I am going to hunt I sight in at distance.

Al