Personally , I don’t think you kneed to buy anything. All you have to do is, place the rifle on a cradle or stabilize it on sandbags so it doesn’t move. Remove the breach plug and keep the action open so that you could see thru the barrel. Place a target at 25 yards. Hold the rifle steady o/c of the target and then dial the scope to the same location on the target. This should be close enough to hit paper when you make your first shoot. Then it’s just a mater of finishing the job... Good luck.