Just slap it on your other rifle, get the rig set up in a gun vise so that you can look down the bore and center your bore view on a paper bullseye at 25 yards...then -without moving the rifle- move your scope crosshairs on to the bullseye as best you can...then fire at least 2 shots for a group. Now- without moving the rifle move your cross hairs to target the first group you just fired..........then take it to the 100 yard range and check out a 3 shot group and re-adjust.