How To Measure Scope Height

If you are a hunter or someone who likes to shoot at targets, then likely you own a rifle and a scope. The questions that seem to come up regarding a rifle scope is where should it be mounted and how to measure scope height?

How To Measure Scope Height

Image by Sgt. 1st Class Victor Aguirre | Public Domain

Scope Mounting Height Is Important

Firstly, the way a scope is mounted onto the rife is quite important. Having the proper scope height can affect the accuracy of the weapon in several ways. For instance, different kinds of scopes need to be mounted at different heights. An optic scope, for instance, should be mounted low so none of it touches the weapon.

The lower a scope gets mounted, as well as the closer a scope is to the axis of the rifle’s bore, the more likely it gives you a more consistent sight picture so long range shots are more accurate. Plus, the height of a scope also determines its useful life. For instance, The higher up it is placed, the more torque and force that gets asserted onto it during a recoil. This can eventually break or wear out a scope.

Plus, lower mounted scopes are generally more comfortable for the shooter, because it affects how your check sits against the rifle. You want a good check resting height when you look through the scope and if it is too high that won’t be possible.

Scope Height Determining Factors

The objective lens, otherwise known as a bell housing, is what determines your scope height. It’s the widest section of the scope which sets in the most forward position on the scope. These are usually measured in millimeters and the most common is the forty millimeter size. However, it also comes in sizes from 28 to 50 millimeters, depending on what you end up using the scope for.

Most scopes for rifles are ID’ed using the format: Lowest magnification -highest magnification x objective lens diameter in millimeters. So, in order to get a basic notion of the scope height measurement, you need to use the objective lens diameter, then add two to four millimeters to account for the scope body’s thickness. Then, you divide that by 2 and that tells you the scope’s height.

If you need a number that is more accurate, then you need to measure the scope body’s diameter at the objective lens and then divide what you get in half. If you need to convert inches to millimeters, then multiply the measurement by 25.4.

Other Ways To Measure Scope Height

These measuring methods for getting the scope ring height don’t consider factors like the clearance for the bolt action, open sights, etc., so extra space would be needed for those cases.

One question sometimes asked is how to find the scope’s center height to the center line of the bore, as this measurement is used in a lot of ballistic programs. Here is how to do that:

  • Measure diameter of the bolt divide that in half.
  • Measure the diameter of the scope’s tube and then divide that in half.
  • Measure how far it is from the top of the rifle bolt to the bottom of the rifle scope.

Ring Height Is Important

Ring height is one factor some people forget about when they are putting a scope on their rifle. If you put it on too high the accuracy will not be that good, since it messes up the check height you end up with. And if you put it too low, the scope ends up hitting the rifle’s barrel, so that’s not good either. It needs to be somewhere in the middle of these two factors. Here’s the best way to properly measure the height of the scope ring:

Firstly, you want the ring’s height starting from the receiver contact point to the ring’s center, or the ring cradle’s bottom. You can use a ruler to measure from the bore’s center (or at the stock’s top if this is a bolt action weapon) to the objective lens’ center (some folks measure to the windage knob’s center). For something a bit more accurate, measure the bore’s diameter and divide by two, then measure the objective lens’ diameter, then divide by 2. Then measure how far it is between the receiver and scope and add that amount to the other two measurements.

Your mounted rings must be the lowest number possible and not have the scope touch the rifle. Plus you want the view through the scope to be optimal for your planned use. So once you have mounted the scope, take a look in it and double check that it meets your needs.

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