How to Shim a Scope? Step By Step Guide 2024

Scopes are useful, but when they start getting issues, they become a headache. One of those issues is the misalignment which causes barrel drop. So, you try to use the turret to get the adjustment right, but windage and elevation fail to get your scope perfectly adjusted. 

In this situation, you will be helpless – and the conditions become worse when you’re taking part in any shooting competition. Then comes scope shimming to rescue you. Actually, shimming of scope is a short-term remedy that adjusts your scope in a way that you tend to see everything clearly.

But there are many people who don’t know how to shim a scope. If you’re also one of them, then don’t worry as I have got your back. In this guide, I will guide you through everything that you need to know about the shimming of scope.

Related Article: Common Athlon Scope Problems

Introduction: What is Scope Shimming?

Scope shimming is the process of adjusting the angle of a rifle’s scope to align it with the bore axis of the rifle. It is a short-term or temporary solution to correct misalignments that occur due to harsh usage, wear and tear, etc.

As you know when it comes to shooting, accuracy is something that you love. But if your scope is misaligned then the chances are high that you won’t be able to hit the target accurately. In such cases, the shimming scope becomes a must.

But the question is how is it done? You’ll have to put or place material in between the scope and the rifle’s receiver or base. These shims (material that you aim to place between the scope, and the rifle’s receiver) are available in different thicknesses, typically ranging from a few thousandths of an inch to a few hundredths of an inch.

One thing that I must say is that shimming a scope is not a very tough process – and everyone who has scope can do it quite effectively. In fact, your scope is doing a fine job, you still learn shimming as it will help you when your scope gets misaligned due to any reason.

How to Shim a Scope? Step By Step Process

Here comes the most important part of this guide – in fact the section for which you’ve come. In the section below, I will explain how you will be able to shim your scope effectively in the easiest possible steps. So, let’s dive into it.

1- Materials Needed for Scope Shimming

Before you start a process, first of all, you will have to make sure that you have all the tools, and equipment that you’re going to need for the scope shimming. If you don’t have these tools, I highly recommend you arrange them: otherwise, you won’t be able to complete the process. In the section below, the list of required tools is mentioned

• Scope rings
• Shims
• Level
• Torque wrench
• Shims (Material)

One thing that can come into your mind about the material that you’re going to use for shiming. Look, the shimming material must be thin, and flexible. First of all, keep in mind that there is no hard and fast rule about which material you should use for shimming. 

You can use cloth, rubber, brass, plastic bottle pieces, aluminum prices, etc. But I recommend you to use strong, durable material for the shimming. So, aluminum material is going to give you perfect results. Again, there is no hard and fast rule about which material you should use. Also, make sure to choose the material with the right thickness.

2- Measure the Correct Size for Your Scope Rings

The second thing that you’ll need to do is to measure the correct size for your scope rings. This is not a very hard task, as you can do this by measuring the diameter of your scope tube with a caliper. When you measure the size of the scope ring, it will ensure that you get suitable, well-sized scope rings.

3- Remove the scope from the rifle

Once you have the correct size of the scope rings, remove the scope from the rifle. This will make it easier to install the shims and properly align the scope. You’ll have to unmount the scope, don’t do anything to the adapter which holds the scope on the rifle. 

4- Installing the Shim

In order to install or place the shim, you will have to use a wrench to gently remove the scope from your rifle. When you do that, a ring will come off too. But don’t worry, leave the rings at the bottom where they are.

Here comes the most important step as you’ll have to install the shim. So, use a shim material and place it on the back ring of the scope. This helps the scope point exactly where you want. Make sure to put these thin shims on one at a time. 

If you need to adjust things more later, you can add an extra piece at the back. This helps you fine-tune things without starting all over. There are many people out there who put many pieces which I don’t recommend you to do. Using too many shrimps makes things wobbly.

5- Bolt the Rifle Scope Back and Level

After installing the shim, bolt the rifle scope back onto the rifle. You should use a torque wrench to tighten the screws to the manufacturer’s recommended torque settings. This is not the end. You must check the level of the scope, and rifle and ensure that the scope is mounted at the right height.

6- Test the Alignment

Once you have done the shimming and mounted the scope back on the rifle, then I highly recommend you test the alignment before using them for shooting. When you test the alignment, it will give you an idea about whether you still need to adjust the scopes or not. 

If you are unable to focus perfectly, then I highly recommend you put one more shim or remove one shima and check its alignment. By doing this, you’ll be able to align the scope properly.

Troubleshooting Common Issues while Scope Shimming

If you’re going to shim the scope for the very first time, then chances are high that you’ll make mistakes in completing the process. But you don’t need to be worried as I have got you covered. In the section below, I am going to mention a few common issues that you can encounter. By knowing them, you’ll be able to shim the scope confidently.

1- Over-Shimming

One common issue when shimming a scope is over-shimming. This occurs when too many shims are used, which I have already mentioned. When you use too many ships then the scope gets too high. 

Point to Remember: Over-shimming can lead to a number of problems such as difficulty in sighting in and decreased accuracy.

This is why I highly recommend you use a lesser number of shims, and then test the alignment to check if your scope is going to a good focus or not. In case you fail to see clearly, then you can add more shims accordingly.

You should also measure the height of the scope rings and the scope itself. If you have already over-shimmed your scope, you will have to remove some of the shims to lower the scope. Don’t be in a hurry and complete the process carefully.

2- Alignment Issues

Another common issue when shimming a scope is alignment problems. This occurs when the scope is not properly aligned with the rifle barre so it will cause the bullet to hit off-target. To overcome this issue, make sure that you install or place the shims carefully.

After shimming a scope, if you are still experiencing alignment issues, then you will need to adjust the scope’s windage and elevation settings. This will remove your issues. However, if it does not solve the problem, then I recommend you to re-shim the scope correctly.

Also Read: Can You Use A Rifle Scope On A Pellet Gun?

Benefits of Scope Shimming – Why Should You Shim Scope Rings?

Shimming scope rings is a process of placing a thin strip of material between the scope and the base to correct alignment issues. But the question can pop up in your mind: why should you shim scope rings? But don’t worry as I am going to give you some potential benefits that will help you understand the importance of scope shimming.

1- Saves Time

Shimming a scope can save time and frustration by allowing the shooter to zero in on their target more quickly. Keep in mind that if you don’t do shimming of scope, then you will have to make multiple adjustments to the scope’s windage and elevation to get the desired zero. By shimming the scope, the shooter can get closer to the desired zero from the start. This will save you time from doing multiple adjustments.

2- Budget Friendly Solution

Shimming a scope is a budget-friendly solution to fix alignment issues. Instead of purchasing a new set of rings or base, shimming is done with a small piece of material such as aluminum foil. So, this makes it a cost-effective solution for those who want to improve their accuracy without spending much money.

3- Make Adjustments according to your will

Shimming a scope allows the shooter to make adjustments according to their preferences. By adding or removing shims, you will be able to adjust the scope’s alignment to their liking. This can be beneficial for those who prefer a certain eye relief or for those who shoot at longer distances.

4- Won’t need to buy a new scope

There are many people who stop using scope when it causes alignment issues. I have seen many of my own friends who prefer buying new scope when their old scope gets issues. This adds additional cost to your shoot journey. 

But when you know how to shim a scope, then you won’t need to spend a handsome amount of money to buy a new one. The reason is that your older scope will get better when you shim it and you will be able to shoot with accuracy.

How to know if I need to Shim my scope?

Shimming a scope is a great way to adjust the position of your scope when it is mounted to a gun. But how do you know if you need to shim your scope? This question is very common among the shooters. In the section below, I am going to give you some points where you should consider shimming your scopes.

• The most common reason to shim a scope is when you are in the field and the scope has been knocked out of alignment. Suppose you’re taking part in a shooting competition and out of nowhere your scope gets misaligned. This could happen from a drop, an impact, or other such damage. This is the time when you will have to shim a scope to readjust and align it properly. The shimming scope does not take much time, and you’ll be ready to shoot within a few minutes.
• Another reason to shim a scope is if you are having trouble sighting in your rifle. If you find that you are running out of adjustment on your scope’s turrets, then in such a case, shimming the scope will help you get the additional adjustment you need. But one thing that I would mention is that you should take shimming as the last option. If your scope gets out of alignment, then try to adjust it by moving it or by using a turret.

Frequently Asked Questions