A video production of this procedure can be viewed here: ATAC TV
Checking the Scopes Mechanical Zero:
The Reticle in the scope may not be centered, meaning that the adjustments for elevation and windage are not centered. You need to find out if your scope has the equal number of clicks up and down as some scopes don’t but most do. If your scope has equal clicks up and down and side to side just turn the particular turret all the way one way and then count the clicks in the opposite direction. Once you have the number of clicks just divide the number by 2 and turn the turret back that number of clicks. Do this for both turrets.
If your scope is manufactured with uneven elevation adjustment up and down then you will have to place the scope in v block or make a V shaped cut in both ends of a shoe box. Rotate the scope while watching the reticle and a spot on a distant wall, say 50 yards. If the reticle does not stay centered on the spot as you turn the scope, you need to adjust the elevation turret so that the reticle stays as centered as possible while rotating the scope.
Another method for mechanically centering the scopes reticle is to place a mirror in front of the objective lens. Make sure the mirror is flat on the objective lens bevel. If the scopes reticle is not centered you will see two reticles when looking into the eye piece. Turn the turrets till the two reticle images overlap.
Mounting the Scope Rings:
1. Place the lower ring halves on the scope base mount, but do not tighten the cross bolts at this time.
2. Place a machined bar the same diameter as the scope body on the lower ring halves and align the rings until the bar can be moved back and forth without binding. The scope body can be used but not recommended. Tighten the scope ring cross bolts to the recommended torque. Check the alignment of the rings one more time with the machined bar.
3. Making sure the lower ring halves are clean (you can use alcohol). Use some dry erase marker on the rings and once dry lightly rotate the scope body on the rings and check the contact area. If the scope does not contact the ring fully, the scope rings will have to be lapped. This should be performed by a qualified gunsmith.
4. Once the contact area has been verified as perfect, clean the rings one more time. Place the scope on the rings. Clean the upper ring cap contact surface and place the caps over the scope body. Make sure the ring screws are clean, insert the screws and lightly tighten. The scope must still be able to be move at this time.
Adjusting the Eye Relief:
This is probably most important adjustment you make to the scope on your precision rifle. This will affect every shot you fire from here on out so take your time and get it right.
The scope needs to be adjusted so that the scope is as far forward as possible while maintaining a perfect field of view through the scope with no shadow around the edges. You want a perfect scope picture with the image all the way to the edges of the lens. This needs to be accomplished while maintaining a perfect cheek weld without “chicken necking”. Once you are in a comfortable position, move the scope back and forth to obtain a perfect field of view. DO NOT MOVE YOUR HEAD once you establish your cheek weld! Your head is supported by the butt stock, not your neck. There will be roughly a ½ window to get the correct eye relief. The scope will usually be positioned around 3 inches from your eye. You do not want to get a black eye from the scope under recoil. Check this eye relief several times. Try this to verify the scopes position; Close your eyes and mount the rifle to a perfect cheek weld. Open your eyes and see what you’ve got. Repeat this several times form all shooting positions and take your time. (You can place a piece of electrical tape around the scope body to mark the scopes fore and aft position within the scope rings).
Adjusting the Scope Reticle Alignment:
There are commercially available tools to aid in this procedure. The method described below uses readily available tools.
1. One method is the plum line method. You will need at least 25 yards of space, a carpenters level, a plum line and a rifle rest or sang bags to support the rifle.
2. You will first need to tighten the scope caps side to side to around 5 inch pounds, maintaining and even gap side to side. (This will maintain the scope ring alignment for the next step).
3. Loosen the the scope cross bolts and gently remove the scope and place a level on the top of the scope rail. When the rifle is perfectly horizontally level, secure the rifle so there is no possible side to side movement.
4. Re position the scope to the base. Gently tighten the ring cross bolt nuts alternating front and back till manufacturers specified torque is reached. Make sure the rifle does not move.
5. Gently loosen the scope ring cap screws so that the scope body can be rotated with slight pressure.
6. Now hang the plum line at least 25 yards in front of the rifle. Look through your scope and align the vertical cross hair of the reticle with the plum line by gently rotating the scope.
7. Gently tighten the scope cap bolts finger tight maintaining an even gap side to side on both the rings. Now tighten the ring cross bolt nuts alternating front and back a little at a time until the manufactures recommended torque is reached.
There are commercially available tools to facilitate this procedure.
Focusing the Ocular Lens:
Look through the scope with a plain white wall in the background. Adjust the eyepiece focus ring until the reticle is perfectly clear. You are focusing the reticle only, not the wall. Only look through the scope for around 4 seconds at a time or your eye will compensate. If you are going to wear shooting glasses, wear them while doing this. If you have a scope that does not have a locking ring tape the eye piece to stop it rotating. If you are going to install flip up lens caps install the cap and tape it.
You can bore sight the scope by different methods. Use a collimator if you have access to one. You can use a bore laser . Or the caveman method done at the range! This is the least preferred method. First, you remove the bolt and place the rifle on its bi pod or sand bag. Look down the bore and aim the rifle at a target at 100 yards if possible. Do this a few times to make sure your lined up. When you are satisfied you are on target look down the scope and center the cross hairs on the target by adjusting the turrets. Look down the bore again and then down the scope, once satisfied that the bore and the scope are at the same place on the target turn the elevation turret up 2 ½ MOA.