Scope 101: Part 11 – Mounting, Mechanical Zero and Lapping

March 4, 2016 by Calley Carpenter


Mounting the Scope

Like purchasing a quality scope, don’t be cheap with your mounting system or it will cause you to have problems in the long run. Doing proper research, finding out what kind of mounts are available for your rifle and knowing how to properly mount a scope to your rifle can be a bit time consuming but ultimately rewarding. Remember that your choice of mounts is what connects your scope to your rifle. If you have a quality rifle and a quality scope but poor mounts that allow the scope to slide, loosen up over time and move with recoil or don’t hold true they will cause you endless frustration and can make you miss the shot of a lifetime.

Mechanical Zero

This is the term used to describe the exact center of the mechanical range of adjustment for your scope. Even if you have purchased a brand new scope, it is recommended to confirm mechanical zero. All you have to do is to rotate your windage adjustment all the way to the stop, then count the clicks as you rotate the windage knob in the other direction. Count how many clicks or turns, divide that number in half and count that number back toward center. Then do that for the elevation adjustment. This will ensure that you have the scope reticle centered in the scope tube and allow you to make adjustments from a known point.

Some scope mounts require a set amount of torque for the screws. I strongly recommend that you purchase or acquire a torque screw driver. Once again, the scope mount is a vital piece of your scope. At any time, if you feel overwhelmed, just stop and take the rifle to a qualified gunsmith or professional for help. Better to pay a professional than to mess up a valuable scope or rifle.

Be sure to understand how your scopes mount works and always following the mounting instructions for your specific mount. I always test fit before I tighten anything. It is important to put the rings as far apart as possible. This will distribute the weight of the scope and allow for greater balance and stability. Be sure to check each scope ring for raised ridges or any manufacture defects that could cause pressure on the scope tube.
When you tighten the screws, be sure to use a cross over technique when you tighten them. Do not screw one screw in all the way and then do another one the same way. This is similar to tightening lug nuts on a vehicle tire. Tighten a turn per screw, work your way cross way to the other screws and be sure to do both the front and rear scope rings screws. Once all screws are snug down in the scope rings you can torque to specifications, if needed. You will be screwing and unscrewing these screws especially if you lap your scope so be sure to use the right screw bit size and be careful not to cross thread the screws.


Lapping the scope to the scope rings is a way to increase precision and to avoid scope misalignment issues. This operation might seem complex but it is not.

When you lap the scope rings, you basically are ensuring proper alignment of the tube, preventing any flex or distortion, tweaking or bending. Misaligned scope rings can dent the tube, cause adjustment issues by putting abnormal pressure to the scope tube or distort the reticle. It is very difficult to see any misalignment with the naked eye. A lapping tool will provide a visual indication of any misalignment.

There are point to point lapping alignment rods and bar versions. You use the alignment rods to ensure proper scope alignment. There are basically two pieces to a lapping kit, the alignment rod set and the lapping tool. The alignment rod set is either 2 pieces of metal with a point at one end or a bar. The lapping tool piece is a solid rod with a handle to hold and rotate the rod in the scope mount. Be sure to have the lower rings mounted to the rifle then put the proper sized alignment rods into the cradle of the lower scope ring and mount the upper rings. They make 1 inch and 30mm lapping kits, be sure to buy the right one for your scope and rings.

You mount the alignment rods in the scope mount just like a scope. If you are very lucky, there will be no misalignment of the points. Usually there is, so that is why you bought the lapping tool. Remove the alignment rods and mount the lapping tool in the scope rings. Remember, you do not want to be too aggressive as you smooth the inner part of the scope rings. You can’t add material, so remove it slowly.

The lapping compound used should be very mild. Once you have the lapping tool mounted and the scope rings properly tightened, use the lapping tool handle to rotate the lapping tool in the mount. This will remove any burs, smooth the inside of the scope rings and align the two mounts to provide a straight cradle for your scope tube. Unscrew the rings, check for alignment and repeat as needed. This process might sound excessive but you have a lot of variables in the scope mounting process and this will eliminate most of them if done properly.

At this point, you should have the scope mounted, the screws tightened but not finally secured, the mount lapped if needed. The scope mounts should be as far apart as possible; the scope should not interfere with the action and it is time to adjust for eye relief.

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