The way and method you mount your scope is incredibly important. An optic-equipped rifle is designed that way to gain the most possible precision possible.
So, mounting an optic improperly goes against the grain and point of the weapon in the first place.
Improper mounting can refer to a variety of different things (rings vs. 1-piece mounts), but for this article, we are going to talk about scope height, proper scope height, and how it affects accurate shooting.
Go As Low As You Can
Different scopes should be mounted at different heights, and preferably you want to mount an optic as low as possible when it comes to precision shooting.
The rule of thumb is typically a scope should be mounted as low as possible, without any portion of the scope touching the barrel or any portion of the rifle.
However, some tactical applications may call for a higher scope height for different reasons particular to their objective.
The lower the scope is mounted, and the closer it is to the axis of the bore of the rifle, the more likely it is to provide the consistent sight picture required for accurate long-range shooting.
Another factor is the longevity of the scope’s life. The higher the optic is, the more force and torque will affect it during recoil. On higher-powered rifles, this can eventually wear out the scope or simply break it.
You Want Shooting to Be Comfortable, Right?
A lower mount is also more comfortable for most shooters. The majority of rifles will have a low comb or cheek rest. When you mount a scope, you should be able to get a good cheek rest on the rifle and be able to look through your optic.
If the scope is mounted too high, you will not be able to see through the scope when using a cheek rest properly, and this requires you to lift your head off the cheek rest and attempt to use the scope. This is not very comfortable and can degrade accuracy.
What determines scope height is the objective lens. The objective lens is, also known as the bell housing, is the widest portion of the scope, at the most forward portion of the scope.
Objective lenses are commonly measured in millimeters, and the most common is the 40 mm objective lens. The 40- or 42-mm objective lens is the best compromise between light transmission, optical clarity, and size.
The 40 mm objective lens can be used with low-height scope mounts and rings on most rifles. Your average barrel and chamber profile is low enough that there is no issue using low-scope rings.
However, heavier barrels, known as bull barrels, are often too thick to allow the use of low-scope rings with a 40 mm scope. 50 mm objective lenses provide a high level of optical clarity and a lot of lights transmitted through the optic.
The trade-off is the requirement of high scope rings on most rifles and extra high scope rings depending on the barrel and chamber profile.
These wide lenses may transmit more light but require either an adjustable cheek rest or a specialized stock for comfortable shooting. Any high-profile optic should be an extremely high-quality model.
Smaller optics with a 28 to 36 mm objective lens require low mounts, and for even smaller optics, like 20 mm objective lenses, you can use extra low-scope rings.
Extra low scope rings, however, lead us into our second portion of proper scope height, mitigating factors.
On a bolt-action rifle, you have to have bolt clearance to manipulate and reload the weapon. If your scope is mounted too low and your bolt is too long, you’ll find yourself at an impasse.
Depending on bolt size, you may need to mount a 40 mm objective lens onto a medium mount to gain proper clearance.
If you are mounting an optic on a weapon that uses an external hammer, like the Winchester 94, a Marlin 336, or a single barrel rifle like the H&R handi rifles, you’ll need clearance for the hammer to move back and forth. These are important considerations to remember.
If you are using a modern sporting rifle like an AR 15 you may desire to co-witness with your iron sights in case your optic dies. This may require a higher mount, but largely depends on the height of your front sight.
Likewise, hunters using shotguns as slug guns may desire a higher see-through mount so they can use iron sights at close range. These are personal considerations one must consider as well.
Proper height will be dependent on your weapon, but again, the lower, the better. This is, of course, a general rule of thumb, and it’s one you should follow. If you can’t go low, go medium. If you can’t go medium, then you have to go high.