How to buy the correct scope rings?

It stinks when you go to mount your new optics and realize you have the wrong-sized rings. After this article on how to buy the correct scope rings, you will not run into this unfortunate situation again.

No matter how many times I rewrite this article, it always seems overly complicated. Bear with me; you will realize it’s not a big deal after doing it the first time.

Before we begin, there are certain things that you will need.

First, you will need to know the diameter of your optics tube and bell. The second thing is the diameter of your barrel. And the third is the height of your rail/mount. Finally, you must select the type/brand of rings you want.

I am going to be using my own numbers for demonstration purposes.

We will be using an online calculator. (Click here) to follow along.

After the demonstration, you will put your numbers into the online calculator and know the correct size.

Today I will be using my Vortex Golden Eagle and their Precision Match Rings. I will be mounting it atop a Borden Accuracy Rail.

Step one

The first thing you will need to do is enter your objective lens diameter (bell).

In my case, that would be 52 mm.

Step two

If you have a cap, you will need to know the outside diameter of that. Since I don’t have one in my case, the number would be 0.

Step three

Remember when I said that you would need to pick out what company product you want to use? This is where that information comes in handy.

When I go to the Vortex site and look at their precision match rings (the type I selected), I see four different selections for height.

I prefer my optics to be as low as possible without coming into contact with the barrel. This decision is up to you. In my case, I will select their lowest ones (0.87 inches).

Step Four

Contact the manufacturer and get your mount/rail height to its tallest point (Rear). I don’t recommend measuring it yourself because it’s a critical number. Even being slightly off can mess things up.

In my case, it is .415 at the rear.

Then get the diameter of your barrel (1.25″ for me).

Step Five

Time to do a little math:

Add the mount/rail measurement to the barrel height.
.415+1.25 = 1.665

Here is where most people make a mistake. Suppose you have an off-set rail; that has to be factored in:

Rail cant/MOA x mount length;
20 MOA x 1/60 = 0.03 (inches of height lost).

The calculator can do this for you. (Click Here)

Now we subtract two numbers to get almost to home plate. 1.665 – 0.03 = 1.635.

Step Six

Enter your numbers into the online calculator. Then hit calculate.
You will then get a Pass or Fail result.

If you get a fail, then go back and select a larger ring size and rerun the numbers.

If you get a pass, you are good to go.

Back to Rifle Scope Series

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