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How to Lap Scope Rings – Detailed Guide from Firearm Specialists

how to lap scope rings
Written by Erik Himmel

Gunsmithing is a precise art. Your average Joe might be a bit at sea here. The weakest link in a shooting system is the connection of the riflescope whether the long range or the hunting or the rimfire or the thermal scope to the firearm. Scope mounts, rings, and bases make up this connection and unless these are fitted to a high degree of precision, even your high-end scope and rifle combination is pretty useless. In this article, we endeavor to methodically explain how to lap scope rings, an integral lesson for the health of your scope and for accurate shooting.

What Is Lapping?

The procedure of lapping in layman’s lingo is taking two or more surfaces, putting on some sort of abrasive compound between them and generate friction between the parts. The desire is to smoothen and polish the surfaces and the process profiles the surfaces so they fit together better.

Lapping increases the surface contact between the scope tube and ring, and aligns the scope rings. So how is it done?

The base and rings are assembled on a steel lapping bar, the abrasive compound, silicon carbide, aluminum oxide or alumina, and boron carbide being commonly used, is coated on the bar. The rings are tightened until the bar can move with resistance. The bar is then worked back and forth. The bar in conjunction with the compound knocks off the high spots and uneven patches polishing the ring surface in contact with the bar. Lapping is a sound practice increases the performance of some kinds of mounts especially windage adjustable ones.

how-to-lap-scope-rings-1

How to Lap Scope Rings the Right Way?

Getting a professional to do the job of lapping scope rings will cost you an arm and a leg. DIY is the answer to get going, buy a Scope Rings Align Lapping Kit. It’ll set you back by about $70 which is a cheap way to get the job done and also learn firsthand about your prized rifle.

Things Needed for The Job

  • Scope Ring Lapping Kit
  • Allen key, most probably provided for your rings by the manufacturer
  • Polishing compound
  • Paper towels
  • Marker pen to label the ring sections
  • Screwdrivers

Scope Rings and Ring Height

Scope Rings and Ring Height
Scope Rings and Ring Height 2 

Scope-Rings-and-Ring-Height-3
Scope-Rings-and-Ring-Height-4
30mm rings

Measure the diameter of the scope body at the objective lens end and divide that figure by 2.

That is the scope height. Ring height varies from one manufacturer to the other. That is because of the method of measurement as shown above.

Ring heights range from 26mm, 30mm, 34mm, etc. in incremental steps of 4mm.

Vertically split rings offer greater contact.

Positioning The Scope

It is very important that the scope is stable while doing the lapping. You will require a padded bench fly to anchor the barrel of your rifle firmly. A perfectly placed rifle scope will enhance your shooting experience to a great extent.

Checking The Alignment

  1. Position the scope rings in place.
  2. The alignment bar goes into the rings, tips not touching but nearly.
  3. Secure the alignment bar to the top rings and screw tight.

Out of alignment
Aligned
Aligned
Aligned

Marking The Rings

Do not mix up the rings after lapping is completed. Mark them However you feel convenient. Don’t even reverse them, left for right or vice versa. They must be put back exactly in the same position.

Marking-The-Rings

Using The Lapping Bar

1. Remove the alignment bar. We are ready to embark on the exercise of lapping the scope rings.

2. Coat the rings and lapping bar with the polishing compound.

Coat-the-rings-and-lapping-bar-with-the-polishing-compound

3. Now we fit the lapping bar, or as some call it, lapping tool.

lapping-tool

4. Put back the top half of the rings back and tighten them. An important consideration here is not to tighten the rings too tightly or you may damage the rings. The lapping bar should offer very slight resistance only.

5. Move the lapping bar forward and backward for about 30 times. You can feel the motion easing smoother. Then tighten the holding screws at the top of the rings a little, and continue moving the bar. A 100% contact with the lapping bar is an impossibility. About 80% is achievable which is sufficient for flawless alignment of the scope.

The Moment Of Truth

Take off the rings completely. Feel with your fingers the change in the smoothness.
The-Moment-Of-Truth

Cleaning The Rings

Using a water spray, clean the rings thoroughly to get rid of compound remnants and lapping debris. Dry with a paper towel.
Cleaning-The-Rings
Your lapped scope rings are as good as new with proper holding power due to increased contact.

Tips for Lapping Rings for Alignment

  • Even if your scope is newly purchased, the rings are seldom machined properly.
  • Before cleaning with water, using a paper towel, clean off the rings.
  • Don’t do a rush job on the cleaning after completing the lapping. It could lead to problems next time around
  • Rings that are not aligned will exert a force on the rifle scope distorting it Now that you have a scope lapping kit, you can check the alignment every once a while.
  • Measure the scope height and adjust it to ensure compatibility with lens and rings.
  • A bent scope plays havoc with accuracy as the barrel is also affected by the scopes’ distortion.
  • Using a light grease, coat your alignment tools, wrap them in a clean cloth and keep it in a safe, dry location for next time.

Our night soldier is on the prowl with his refurbished, trusty riflescope! No quarry is safe. Now that you have the complete lowdown on how to lap scope rings, remember that it is a complete process in keeping your scope secure. Most manufacturers claim that their design is unique and tested. You will need to make certain that scratches are not being inflicted on your scope by the contact. The entire process takes under 30 minutes, the reward, a completely scratch-proof scope.

About the author

Erik Himmel

A Part-Time Firearm Instructor

Hi, this is Erik. We all know firearms are dangerous, but only when one doesn’t know how to use and care for them. I have 15+ years of experience with different types of guns and for the last 10 years, I have taught numerous people how to hold and shoot a gun while staying safe and keeping the surroundings unharmed. My neighbors are some of my biggest admirers who enjoy talking to me about their guns, firearms safety and maintenance.

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