Determining the proper scope ring height for your rifle is crucial for comfortable shooting and maximum precision, but the wide variety of mounting systems and the inconsistent ways that many manufacturers label their products can make this process frustrating, to say the least. Luckily, we've broken it down into a quick and easy guide, so if you're looking for a foolproof system for getting perfect measurements, read on.
Why Is Proper Scope Ring Height Important?
Proper scope height is important for several reasons. First and foremost, your accuracy will greatly suffer if your rifle scope is so high that you can't maintain a consistent cheek weld or get a clear image, forcing you to shoot in an awkward position.
In extreme cases, the scope might be mounted so low that it actually comes in contact with the barrel, which can put pressure on the scope, throwing off accuracy and potentially even damaging your optic.
Second, improper scope height can lead to issues with parallax, creating a black halo or "ghosting" effect around the lens that makes target acquisition more difficult. It can also interfere with bolt clearance.
Finally, if you're a precision shooter or enjoy shooting at long distances, knowing your scope height is an important factor in the calculations made by virtually every serious ballistics app.
How Do I Measure Scope Height?
Put simply, scope height is the distance between the center line of your barrel and the center line of your scope. So how do determine scope height? There's an easy way, and a more accurate way.
The easy method involves a single measurement: using a ruler, measure the distance between the center of the bolt housing and the center of the scope. It's not an exact measurement, but it's good enough unless you are trying to make your rifle as compact as possible or trying to squeeze every last bit of performance out of a benchrest rifle.
For the more accurate method of measurement, here are the steps:
- Install your base, rings, and scope.
- Back out the rifle's bolt until it is roughly in line with the end of your ocular lens.
- Using digital calipers, measure the diameter of the rear of the bolt and divide that number by 2 to find the radius (the exact distance from the center of the bolt to the edge).
- Measure the diameter of your scope's ocular bell, and divide that by 2 to find the radius.
- Measure from the top edge of the bolt to the bottom edge of the scope.
- Add these three numbers together to find your exact scope height.
For an AR-15 or any other similar gas-powered rifle, the process is pretty much exactly the same, except instead of taking a measurement the bolt housing, you'll need to pop open the upper receiver and use the diameter of the bolt carrier group instead.
Steps For Scope Ring Height Measurement
Once you know your scope height, you know the minimum distance that your scope's center line needs to sit above the bore. After that, your goal is to find the shortest combination of scope ring and scope mount that is taller than your scope height. For example, if your scope height is 25mm, then you need a ring and base combination that is at least 26mm tall.
Keep in mind that there are two widely used methods of measuring scope ring height, and to properly determine scope ring height, you need to know which one is being used by that particular company. The simplest and most common method is measuring from the base to the ring center. If the combined base height and ring height is larger than your scope height, you're good to go!
However, some scope ring manufacturers measure from the base to the ring edge instead, and this means a little more calculation is in order. In this case, when adding the base and ring height together, also add either 12.7mm or 15mm to the total, depending on whether you are using a scope body with a 1 inch tube or a scope body with a 30mm tube, respectively.
Choosing The Right Rings For Your Scope
Choosing the right scope rings and the right base comes down to multiple factors: what kind of mounting platform your rifle uses, receiver height, how large your scope is, and which scope ring height feels the most comfortable.
As a general rule, your rifle's mounting style is going to determine the type of rings you will buy. Weaver rings pair with a weaver rail, dovetail rings with a dovetail base, and so on. The exception is a picatinny rail, which is compatible with virtually any set of rings and other accessories you are liable to come across.
When factoring in scope size, you'll need to know your scope height and the diameter of your scope tube. Most manufacturers offer options that accommodate all of the major scope tube diameters, so the real key is making sure you have enough room to accommodate the objective lens diameter - especially if you plan on using flip-up lens caps.
Unfortunately, this is where things can get a bit tricky. Many scope rings come in either low, medium, or high, and these numbers can vary wildly from one manufacturer to the next. That means you may need to look at the manufacturer's website to see if they list exact specs, or be ready to do a little trial and error.
Thankfully, some ring sets list their actual height measurements, which makes it much easier to confirm that you'll have enough room for your scope. While your goal is ideally to pick the lowest scope rings possible in order to minimize the distance between your bore and point of aim, it ultimately comes down to which height feels the most comfortable to the shooter.
The only other major things you need to consider when measuring scope ring height are bolt action clearance, access to the breech, room for lens caps, and room for any other accessories you want to add.
Measuring scope height can be a challenge, but we hope this guide takes some of the frustration and guesswork out of it and helps you find the the combination of scope, rings, and base that are the best fit for your rifle.
If you have any questions or need any clarification on the process, sound off in the comments and let us know! And if you're looking for a new scope, head on over to our list of the top 8 scopes under $1000!
Happy shooting, and see you at the range!