You now have your new scope just installed on your rifle and are ready to do some shooting. There is just one problem...that is the scope will normally not hit anywhere near your aim point unless you sight in your scope. The first step in this process is to bore sight your scope using a bore sight tool designed just for this purpose. Bore sighting is simply a means of aiming the bore of the rifle at the aim point (bullseye or any other spot on the target). With the bore sight tool projecting a laser beam at the aim point the scope can then be adjusted with the elevation and windage knobs (turrets) to bring it into alignment with projected laser dot showing on the paper. The bore sighting can be done at shorter distance (25 yards) since it is an approximation of the bullet path, but does not take into account the trajectory of the actual bullet as it leaves the barrel. Once the scope's reticle is lined up with the laser dot on the paper you are ready  for the next step. I equate the balance of this process to fine tuning.

Actual sighting in.

This is where the fun begins. I recommend using a solid set of bags on a good benchrest or preferrably a vise type benchrest that securely holds the rifle from moving. These typically have some windage and elevation adjustment which helps in the  initial positioning of the gun. I personally like to sight in at 100 yards while some shooters prefer a shorter range that will provide the same bullet point of impact due to the trajectory of the particular round you are shooting. As an example, if you shoot your favorite round at 100yards it will also hit the target a the same point by shooting at a closer distance eg; 25 yards. Place no more than 3 shot strings to determine your difference between aim point and point of impact. If the point of impact is grouped at 3 inches horizontally from the aim point then your adjustments will be based on the minute of angle (MOA) for your particular scope.

Zeroing in:

Scopes are calibrated for windage and elevation adjustments in what is known as Minutes of Angle (MOA). For example 1 minute of angle equals 1 inch at 100 yards. Most hunting scopes are calibrated in 1/4 (MOA) increments. The windage & elevation knobs have a knurled pattern on the perimeter with each click of the knob providing 1/4 inch point of impact change at 100 yards. If the first group is centered approximately 4 inches off the aim point trhen you will turn the knurled knob 16 clicks in the proper direction to bring the point of impact into line with the aim point. Th esam holds true for elevation adjustment. Complet your windage adjustment first and then make you elevation adjustments once your on target horizontally. If your point of impact is 2 inches off the aim point you will need to adjust theknob by 8 clicks.If you are sighting in a longer range high resolution varmint scope you may have 1/8 inch MOA adjustments. This provides much much finer adjustments at longer range. This would also be the case for longer range competition shooting.Continue to shoot in strings (groups) of 3 shots to determine tightness of groupings. If your groups are consistantly centered on the aim point you have effectively 'zeroed in' your scope.

Consistant Patterns

The tightness of these patterns is then determined by other variables, such as load, wind, humidity & temperature. In addition, the steadiness of your bench rest (or bags) is in question then your groups will vary in spread of the shots as well as in relation to aimpoint. To eliminate some of the 'human element'. A noted earlier, I recommend a solid vise type of benchrest with elevation and windage adjustments on a cement benchrest table. If your goal is precision target shooting or long range varminting. personally, I prefer a fine crosshair reticle for target with a higher powered scope & large 50mm or higher objective lens. This enables a very precise placement on the aimpoint & prevents the blocking of prior shots by the reticle.

This process is really quite enjoyable if you treat it as a fine tuning of a fine scope anf rifle.