How High Should I Mount My Scope

The riflescope is not a new thing. But going back to the ‘50s, firearms with iron sights were all the rage, while scopes were usually found only in the hands of professionals and rare gun enthusiasts—and that’s because scopes before, were generally fragile and difficult to mount.

Today, an optic-equipped rifle is a relatively common weapon that can be seen at shooting ranges, hunting fields, and warfare—thanks to the advancement in glass manufacturing, standard magnification; the introduction of variable magnification; and most significantly, the development of systems that attach scopes to firearms.

So, high-quality optics these days are precision instruments that require a reliable scope mounting system to keep the scope secured on the weapon and provide comfortable positioning for the shooter.

Scope / Ring Height Terminology and Common Concepts

A scope mounting system is used to securely attach scopes to firearms, avoiding the shifting or moving of optics. There is a lot of different mounting hardware and the most common that you see on rifles, shotguns, or pistols is the scope ring and base setup.

Modern scopes are mounted using two rings and a base. Initially, the scope mounting systems had fixed scope mounts. Still, popular systems now include quick-detach rings and bases, enabling you to move a scope from one rifle to another quickly.

To further understand how mounting systems work—or should work, we break down the components that you should know about.

Scope Rings

Rings are usually made of steel or aluminum designed to affix the scope to the firearm. Depending on the scope’s main tube, they typically come in sizes ranging from 1” (25.4mm), 30mm, to 34mm diameter.

Note that sometimes, people refer to the main tube as “barrel,” but using these two terms interchangeably can cause confusion.

As for the rings’ design, you may encounter horizontal or vertical split style, and many folks prefer the former over the latter.

Bases

The base is the part of the mounting system that is affixed directly to the firearm receiver, and as its name implies, it provides a “base” that supports the rings and scope.

Bases are offered in one- or two-piece design—the latter being the most popular. There are a variety of bases for different models and brands, therefore, you have to choose what fits your firearm, and next to that is your personal taste.

Rails

Rails are mounting platforms that basically function like bases—but the difference is, they are incorporated with grooves or slots that allow sliding or position adjustments of scopes and other accessories.

The two most popular rail systems on the market are Picatinny and Weaver-style. Both are very similar and some aspects, but the most notable difference is the spacing of the grooves.

Weaver rails have closer grooves, offering more mounting positions with less space in between possible slots. Picatinny, on the other hand, has evenly spaced grooves that spread across almost the entire length of the rail.

Next in line are few considerations for scope mounting height that you should know about.

Scope Tube Diameter

One of the crucial information you should know before you even start looking for a mounting system is the diameter of your scope’s main body.

As we’ve mentioned, the size of the scope ring directly depends on the main tube diameter, and scopes on the market today have a wider range of diameters—with 1 inch and 30mm being the most common, and some 34mm, 35mm, up to 36mm.

Objective Bell Size

The second vital measurement is the diameter of the objective bell (the side that points downrange). The rule is, the smaller the objective bell, the lower the rings should be. 

For example, a scope with a 28 to 36mm objective lens require low scope rings, whereas the 40 or 42mm objective lens need medium height scope rings and 50mm, or 56mm will require high height rings to accommodate the larger bell housing.

This ring height options can further expand to extra-low for even smaller optics with 20 mm objective lenses, and to extra high height for gargantuan 60mm objective bells.

Saddle Height

Since ring heights vary from brand to brand and no standard measurement is set for the scale of “extra low to extra high,” some manufacturers use scope saddle height, instead.

The saddle height is the actual measurement of the ring height—the distance from the top of the scope base to the bottom of the tube.

To get the ring’s centerline and determine the proper ring height, add the saddle height—which can also be found in the manual—and the half of the tube diameter (12.7 mm for a 1” scope, for instance).

Bolt Clearance

One of the often-overlooked nuisances on bolt action rifles that use an external hammer is clearance at the ocular (back) lens for the bolt or hammer's free operation.

This problem is especially pronounced on some bolt action when optics are mounted too low and the bolt in its open position, hits the eyepiece of the rifle scope.

Therefore, the solution to a proper bolt clearance is the use of higher mounts.

Base Height

Regardless of whether it’s a one- or two-piece design, generally, it's considered that a 0 MOA base is flat or level with the bore of the rifle, compared to 20, 25, or 30 MOA bases that are canted down in the front toward the barrel.

Standard bases sit slightly higher than the barrel contributing somewhat to ring height. On the other hand, sloped bases are preferred by long-range shooters because they offer more adjustability, while the canted bases can present cheek weld or height problems.

How To Measure Scope Height / How to Determine Scope Ring Height

First, you need to know your approximate scope height before you purchase rings to get your sight as low as possible without touching the weapon's barrel.

The second reason mostly concerns long-range shooting because measuring scope height is vital when shooters use ballistic calculators to help compute trajectory calculations for their specific rifle/set up.

Method 1: Scope Ring Pedestal Height

1. Measure the objective bell (including scope caps).
   
   
2. Measure the diameter of your scope tube. 
   
   
3. Subtract the scope tube diameter from the diameter of the objective bell, then divide by 2, and add 0.1”.
   
   
4. Finally, subtract the height of your base from the previous result.

The result is the optimal ring height for your scope. This represents the height from the receiver to where the ring contacts the bottom of the scope tube.

Other techniques determine the scope center height to the centerline of the bore for ballistic programs.

Method 2: Bore Zeroing

You can make the more exact measurement using a piece of plain white paper and a bore laser.

1. Set your scope on the lowest power.
   
   
2. Secure the rifle in a barrel vise or similar device, facing a wall.
   
   
3. Place the piece of paper on the wall with a small dot or X on it.
   
   
4. Center the crosshairs on the dot or X on the paper.
   
   
5. Turn on the laser and mark its location on the paper.
   
   
6. Measure the distance between the laser mark and the dot or X on the paper to get the exact height of the scope above the rifle's bore.

Method 3: Measuring Ideal Scope Height Directly

Another technique to arrive more precisely at the scope height means using some math and formulas. 

1. Measure the bolt diameter and divide it in half.
   
   
2. Find the scope tube diameter and divide it in half.
   
   
3. Measure the distance from the top of the bolt in the rifle to the bottom of the scope (or where the scope should be on the rifle).
   
   
4. Now simply, add the numbers found in steps 1-3.

Example: 

a) The bolt diameter is 0.700" and 1/2 that of that, radius is .35"

b) Your scope diameter is 30mm (1.181"), and 1/2 of that is .59"

c) A distance from the ring/bases from the bottom of the ring where the scope sits to the bottom of the base is 0.750"

d) The result is .35 + .59 + .75 = 1.69"

What Determines the Height of a Scope? 

The height of scope is determined by the scope's outside objective diameter (usually measured in millimeters), the thickness of the scope cover (usually 2-4 mm), then the rail to barrel clearance, and a rail cant if your base has any adjustment built into it.

Essentially, it would seem that the right way to measure optics height is to get the distance between the muzzle and the line of aim.

As a result, you should get a firmly mounted scope with its largest diameter floating 0.1 of an inch above the barrel.

Does A Shotgun Need Special Hardware?

Though some inexperienced gun owners might think that shotgun scopes need special mounting hardware because of recoil, it’s not true.  There are many high-powered magnum and safari-class caliber rifles with much more recoil power than the most potent shotgun loads can generate.

For example, a 12-gauge shotgun with a 2.75" shell and 1-1/8 oz. load at 1,200 muzzle velocity will generate 23.0-foot-pounds recoil energy, very similar to the .300 Win. Mag, whereas the .500 N.E.  with 570 gr. a bullet fired at 2,150 fps muzzle velocity produces an astounding 74.5 ft. lbs.

It all boils down to, shotgun scopes do not need any unique rings, except for those using one of the specialized “no drill” shotgun scope mount bases.

Pistol scopes are more durable than riflescopes, so they are built to handle the brutal pounding from the most powerful revolvers and single-shot pistols.

As for the height of a pistol/revolver scope, handgunners usually mount the optics with low rings on their barrel, trying to mount a scope on a handgun as low as they can and still clear the top highest point on them.

However, it's not feasible with some revolvers and single-shot pistols due to the comfortable work with hammer or hammer extensions.

How does the type of scope play a part in the height of a scope?

Usually, the size of your optics objective bell will determine your scope and ring height. For instance, long-range optics come with more oversized main tubes (30mm or 34mm) and a sizeable objective lens up to 56 mm and more and require high or extra high rings. 

On the other side, the LPVO (Low Power Variable Optic) features slimmer scope bodies and smaller objective bells of 20mm or 24mm, making them perfect for low height rings and even extra-low scope rings.

Since the scopes vary in length, it may require a higher mounting ring for the longer scope with a smaller objective lens to clear the barrel's chamber portion, which is a larger diameter.

Does the size of the rings affect the height of the scope?

Of course, the smaller the objective bell, the lower the mounting rings needs to be.

You have to purchase rings with appropriate height to accommodate the objective of the scope. Generally, one can determine the required ring height by the size of the riflescope's objective lens.

Obviously, you won’t be able to mount a 56mm objective scope with low height rings, but you can step up a size in ring height and install 40mm objective optics on extra high mounts for some reason.

What If I Have an MOA Mount/Rail?

Using sloped or canted rails (usually 20MOA) canted down in the front toward the barrel will result in moving the objective bell closer to the barrel.

In case you have a heavier than standard barrel contour, having an MOA mount/rail will require you to step up a size in ring height.

Does ring height/scope height affect cheek weld/head position?

Actually, the main reason for finding the right ring height and scope height is getting a proper cheek weld and head position. The height of the cheekpiece will indicate how high the scope will have to be.

Generally, the lower scope height would be more comfortable for most shooters, but either too low or too high mounts won't give a proper "cheek weld”.

If for some reason, you are forced to use high rings where the scope position gets higher, you should install an adjustable cheek rest or a specialized stock to rest your cheek comfortably on your rifle.

Does this / Can this affect eye relief?

The required ring height will also depend on eye relief since the objective sits on the barrel directly related to the proper eye relief.  Some ring/base combos will limit the adjustability, which may limit the amount of eye relief.

If you mount longer rifle scopes with larger than regular eye relief, you will need extended scope rings.

Do I need a bubble level for this? Can it help?

Among other reasons, many shooters prefer their scopes mounted as low as possible because it can reduce the effects of canting, a slight tilt of the rifle, scope, or reticle.

Using a small bubble-level to level your rifle scope would be beneficial if you intend to shoot at longer distances beyond 400 meters or if your scope is mounted farther away from the bore.

When you level your scope, you are trying to make sure the riflescope is on the same horizontal plane as your rifle's action to avoid aiming slightly left or right.

What are the tools and/or materials needed?

Mounting your scope yourself without the help of a professional gunsmith is a completely feasible operation since you can mount optics yourself without any fear of ruining the precision of your rifle.

While scope mounting may seem like an overly technical task, you will be able to do it with few specialized tools.

With any other modification on your firearm, you will need some kind of rig to stabilize your gun. It can be a gun vice or a sturdy bench vice with some aftermarket rubber arms.

Next, you will need a torque wrench to torque the base and ring screws using the manufacturer's specifications. For leveling the rifle, you will need a few small bubble-levels.

You will also need a bit of oil to prevent corrosion and some Blue Loctite to apply at the base screws along with these tools and a little patience.

If you are mounting budget class rings, it is recommended to lap the rings to improve alignment. You will need the alignment rods, lapping rod with handle, and the lapping compound for this process.

You can find market Scope Ring Alignment and Lapping Kits that reduce stress on the scope and improve the rings' grip on the scope. 

What do I need to consider if I’m co-witnessing iron-sights?

If you plan to co-witness iron-sights, you should know that you can't co-witness a magnified optic with open sights. However, with the red dot, reflex, or halo sight installed, you can line up your iron sights.

You can also co-witness a modern sporting rifle like an AR-15 with your iron sights using a higher amount.

There are different mount styles, such as see-through tunnel rings popular among hunters for quick target acquisition and iron sights at close range.

Why is it recommended to mount the scope as low as possible?

When it comes to precision shooting, you want to mount a scope as low as possible because it will provide the consistent sight picture required for accurate long-range shooting.

An optic with minimal clearance above the barrel will be more comfortable for most shooters and enable the line of sight to be closer to the bullet trajectory. 

A lower mount affects the scope life's longevity since that arrangement minimizes the torque on the rings when the rifle is fired.

The hunters and soldiers would also appreciate that low mounted scopes have less chances to get caught on the brush while being carried.

Height Over Bore - What Do I Need to Know?

Height over bore (HOB) or mechanical offset, is a term used to describe the distance between the barrel of a rifle and the shooter's line of sight. The sight height over bore is not specific to magnified optics, but it is also related to the red dot and iron sights.

You can calculate the distance between the optic's center vs. the rifle's bore line if you took half the barrel diameter, add the scope height over the barrel and half of the entire objective diameter.

At normal hunting distances, this sight offset doesn't present too much of an issue. However, it is most noticeable at longer ranges, affecting the trajectory and making the difference between hitting your mark and failing the mission.

Additionally, the bore height differences come into play inside 25 yards with rifles using high-mount scopes like most AR-15 rifles (optics at about 2.6" HOB). With AR-15 zeroed at 50 yards, shots at 5 yards distance targets will hit consistently about 2 and a half inches low because your scope is physically higher than the barrel (height over bore, HOB)

Furthermore, the rifle optics with pronounced height over bore has the increased sensitivity to canting deflection.

Typically, you want the scope mounted 1 to 1-1/2 in above the bore because these rifles will hit closer to POA than an AR-15 with the same amount of tilt.

What Happens If My Scope Is Too High or Not High Enough?

As you might conclude up to this point, the scope objective should never touch the barrel when mounted on your rifle. Of course, it doesn’t mean that you should always look for the lowest mounting. 

It would be best if you mounted the optics where you have a solid, consistent cheekweld to the stock. 

Besides, having the rifle which comes to the eye naturally is essential since you don't have to hunt for the scope when you raise the gun.

The scope must be mounted high enough so the bolt handle has a clearance between the ocular bell and a 90-degree bolt lift. Otherwise, you won't be able to manipulate and reload the weapon.  

The too high mounted scope isn't a good idea, as it might not be comfortable for most shooters and will not provide a consistent sight picture due to the poor cheek weld with a high-mounted optic.

Conclusion 

Many riflemen prefer the lower mounts, but different scopes should be mounted at different heights for accurate target acquisition and shooting.

There are many ring types and base styles, but whatever scope rings you end up choosing, be aware that the rings are the only points between the riflescope and your firearm. Hence, make sure you get the best quality set of rings for maximum performance.