My target rifle scope is a 36x Leupold with target crosshairs. and I will offer this advice. "You can't expect to hit what you can't see". What ever scope you chose for target or long range you will want it equipped with the AO (adjustable Objective) feature.
I use this scope for bench rest and when I'm working up loads for my other rifles. When I am shooting for groups I use square bulls eye targets, black on white. When I sight the rifle I put the square corner of the bulls eye in the upper right quadrant of the cross hair. the vertical part of the cross hair is lined up beside the verticle side of the square bulls eye and the horizontal cross hair is lined up with the lower horizontal side of the square bulls eye. You don;t want to see any white between the cross hairs and the bulls eye. I dont care where the point of impact is, I am only concerned about the size of the group. Only after I'm satisfied with my group size, do I then get concerned with with point of impact and get concerned about the X-ring. I also shoot 5 rounds to get a good idea of group size.
You may ned a bubble level to get your target set Plumb. And using scopes of this power requires good bags and a good rest because it will wiggle an awful lot and at that power it shows up very good.
One other thing I would advise is to , go watch a benchrest match if you can find one. You'll learn a lot just by watching and most of those guys are always willing to talk after they have shot and are done cleaning and reloading.
If you have time to do it twice, then you have time to do it once right and put your name on it