How to Lap Scope Rings?

Buying a rifle scope deserves serious consideration. You will look closely at such things as optic quality, features, functionality, and price. While these priorities are essential, how closely do you look at the type and quality of scope rings chosen?

It is common knowledge that there are a wide choice of scope ring manufacturers out there. What is not so well known is that few produce premium scope rings. The reasons for this and potential issues with rifle construction will be looked at shortly.

From there, the main focus of this article will be how to lap scope rings.

Intrigued? Well, let’s get straight to it to fully understand an often overlooked procedure that really is worthy of attention.

how to lap scope rings

What Does Lapping Mean?

In the firearms world, lapping is used to describe the procedure of “Truing up the inside of your scope rings.” This may be a procedure that many are unaware of or have heard about, but not really looked into. As will be seen, lapping is something all rifle scope users should take seriously.

The very real benefits of lapping apply to both your rifle scope and weapon. Once completed, this process will:

  • Protect the outside of your scope tube from damage.
  • Negate stress on your scope tube: Incorrectly positioned/fitted scopes can affect the internal moving parts of your scope.
  • Help with accuracy by removing any stress the scope tube could be putting on the action of your rifle.

As the article continues, you will see the importance of lapping and how to go about it. By doing so, you will be protecting your rifle from potential damage and securing your scope in a much more solid way. It will also allow you to take advantage of your scope’s full accuracy potential.

What’s The Issue with Most Scope Rings?

When looking to buy scope rings, you are certainly not short of choice. The problem is that premium scope rings with perfectly machined surfaces are few and far between. The reason for this is that they are expensive to manufacture and therefore come with a price tag that many shooters find hard to justify.

Manufacturers get around this by offering a wide choice of acceptably priced scope rings that will “do the job.”

But do they really do the job?

Here are some of the issues that make cheaper scope rings problematic:

In the first instance, the scope rings machined surfaces (where the ring contacts the scope tube) are far from perfect. This is because the majority of scope rings are not perfectly round or smooth. This being the case, issues can be caused at the points where the rings grip your scope tube.

The aluminum tube of a scope is often quite thin. By putting ring pressure on it, there is a chance it will change shape. If this change of shape is bad enough, you could then face problems with the internal workings of your scope. At worst, it can affect the magnification ring and/or the actions of your windage and elevation turrets.

It then needs to be understood that rifle receivers machined with true surfaces are quite rare. On top of these finish issues, you can add one more. The drilled screw holes needed for scope attachment (where your scope base will attach to) are rarely centered perfectly.

These factors on their own may appear slight. However, when you add them all together when fitting your scope, you are looking at potential misalignment and poor fitting. This can quite easily affect accuracy and cause damage to your scope, your weapon, or both.

how to lap scope ring

Lapping Will Prevent These Problems

Truing up the inside of your scope rings will avoid these problems. Once completed, it will prevent any rifle or scope damage and leave you with a scope that is seated correctly.

So, here’s the best way to lap scope rings:

Before starting, safety and a suitable mount need to be addressed. Other optional equipment will be mentioned as the process unravels. As with any weapon maintenance, you should first double-check that your rifle is unloaded. You will then find the whole process a lot easier if you mount it in a vise or shooting rest.

The reason for having your rifle solidly mounted is because you will be applying pressure during the lapping process.

Check Scope Ring Alignment First

Before beginning any sanding or grinding, you should first check the scope rings themselves. You need to see how well they align with each other. This initial alignment check relates only to the scope rings. It is not to see how well the rings align with the bore or receiver of your rifle. A handy tool to have comes from Brownells, their BROWNELLS – SCOPE ALIGNMENT RODS.

These scope alignment rods come in either 1-inch or 30 mm sizes. Alternatively, if you have a variety of different weapons that take different size scope rings, sets with removable sleeves are available. These will allow you to check the alignment of various ring sizes.

Use is simplicity itself and will tell you if your scope rings are aligned correctly or not. You clamp one rod to each ring, and if the points do not touch, it is clear they are out of alignment. This misalignment can be for a variety of reasons, such as mismatched rings, the rings have the wrong bases, or the fact that these bases need shimming.

If for any reason, the rings are not aligned, corrective action is required. This work will depend upon the type of scope rings you are using.

For example…

If the rings have windage adjustments, you will be able to correct side-to-side misalignment. If the problem is vertical alignment, you can use shims under either the scope bases or rail. For those using non-adjustable rings, a straightforward fix should be tried first. This is by swapping ring positions or turning them 180 degrees on the rail.

The aim of this scope ring alignment work is to ensure the rings are aligned as closely as possible before lapping begins.

Lapping The Rings

Once you are happy with the scope ring alignment, then mount the rings firmly to your rifle. If not already done, then place the whole rifle in a vise, shooting rest or support.

Before getting into the lapping work, it is possible to purchase a purpose-designed lapping tool. Sticking with the well-established Brownells quality, their offering is the BROWNELLS – SCOPE RING ALIGNMENT LAP.

Again, this comes in either 1-inch or 30 mm sizes and includes lapping compound. This lap tool works to remove high spots and rapidly true any misaligned or “out-of-round” shaped scope rings. It also works on dovetail rings to turn-in, and rough align them.

how to lap scope ring guide

Quick and easy…

It is designed with dual-handles and multiple, transverse, lapping compound grooves. This gives you complete control, speeds up the work, and ultimately produces faster, more satisfactory results.

Getting back to the lapping work, some shooters prefer to lap rings with the tops installed; others just lap the bottom halves. Both methods work effectively; personally, I find lapping the bottom halves more convenient.

This is because pressure is required during the lapping action, and it is far easier to apply this to the bottom halves. The other factor is that the top halves are more flexible and are quite likely to naturally form fit during mounting.

You may already have removed the top halves of the scope rings; if not, do so. Then, you should apply aluminum oxide lapping compound to the bottom of each ring surface. You may hear that silicon carbide can be used for this. However, in my opinion, it is best avoided because it does not come off the rings very easily and could well tarnish the finish of your scope tube.

Important – Be Sure to Apply “even” Pressure

Steady away! It is important to apply semi-firm pressure consistently and evenly. Do this while working your lapping rod back and forth across the ring surfaces. Patience being that all-important virtue, don’t rush things and don’t force things by asserting too much pressure. It is also recommended that you rotate the lapping rod as you move it backward and forwards. This will help achieve good surface area contact.

Don’t be alarmed when you see grayish goo begin to gather on the rod. This will likely be a combination of metal and interior scope ring finish and is what you want. It tells you clearly that the lapping process is working.

Nearly done…

There is really only one way of knowing when the lapping is completed, which is through a visual inspection. To do this, you need to clean the inside of the rings and inspect them. You may need to carry out this cleaning/inspection several times. That is fine; the aim is to develop a perfect fit, so grab a little more of that patience!

What you are looking for when cleaning the lapping compound off the rings are shiny areas. This is where you have removed the finish and some metal. Many qualified gunsmiths stick to the rule that when 75% of the total interior surface of each ring has been polished off, that is sufficient. No need to argue with the experts; if it is good enough for them, it is good enough for us!

A Thorough Clean is a Must

With the lapping process complete, you should then give the rings a thorough clean. As you will find, the lapping compound does not wipe off all that easily. It may be necessary to use more than a rag. If so, some sort of degreaser will do the job. You should then apply a light, thin film of metal protectant to make up for the surface finish you have removed.

Once this cleaning is done, you are now ready to mount your scope as normal. When doing so, it will be in the knowledge of a job well done.

Benefits will come from a much firmer fit and the fact your scope will hold in place longer during repeated recoil. This, in turn, will help you realize the scope’s full accuracy potential. There is also a very nice plus that comes through the smooth fit you have engineered. This will ensure the body of your scope does not suffer scratches, scrapes, or marks from ill-fitting scope rings.

Looking for Some High-quality Scope Options to Test Your Scope Lapping Skills On?

Then take a look at my in-depth reviews of the Best Deer Hunting Scopes, the Best Low Light Rifle Scope, the Best Air Rifle Scopes, the Best Rimfire Scopes, the Best Mil Dot Scopes, or the Best 308 Rifles Scopes currently on the market in 2021.

Or, check out our reviews of the Best Scout Scopes, the Best 300 Win Mag Scopes, Best Mini 14 Ranch Rifles, the Best Scopes for AR15 under 100 Dollars, as well as the Best Scopes for M&P 15-22 you can buy.

Final Thoughts

Learning the correct way to lap scope rings is something that will certainly add to your overall firearms knowledge. More importantly, it will ensure that your precious rifle and hard-earned rifle scope combine to fit exactly as they should do.

The fact is that most scope rings have not been finished to exacting standards. This means they are not aligned perfectly. This misalignment can cause damage to either your scope, your rifle, or both. Correcting scope ring alignment and moving on with the lapping process will alleviate these problems.

Once completed, you will benefit from a correct, much more solid scope fitment. One that will remain steady on your rifle for a long time to come. It will be stress-free, and this means greater consistency, dependability, and something all shooters search for – the opportunity to benefit from the full accuracy potential of your chosen scope.

Happy, safe, and accurate shooting.

Home » Learn » How to Lap Scope Rings?
About Gary McCloud

Gary is a U.S. ARMY OIF veteran who served in Iraq from 2007 to 2008. He followed in the honored family tradition with his father serving in the U.S. Navy during Vietnam, his brother serving in Afghanistan, and his Grandfather was in the U.S. Army during World War II.

Due to his service, Gary received a VA disability rating of 80%. But he still enjoys writing which allows him a creative outlet where he can express his passion for firearms.

He is currently single, but is "on the lookout!' So watch out all you eligible females; he may have his eye on you...

Leave a Comment