Scope Lapping

Discussion in 'Long Range Scopes and Other Optics' started by MOOSE39465, Sep 3, 2013.

  1. MOOSE39465

    MOOSE39465 Well-Known Member

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    Being that I am newbie to Long Range Shooter I have a great deal to learn, one thing being scope rings. When I purchased a set of Seekins rings for my new build I chose not to lap the rings. This morning after reading a great deal on on scope ring lapping I pulled my scope off and lap my rings. Here is a picture of what it looked like when I first started lapping. You can notice how little contact that I actually had on my scope. I didn't get a picture of the final stages, but it was around 80% contact before I settled. For the newbie's who are just starting out like me and wonder if rings should be lapped or not. Yes they should 100% of the time.
     

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  2. Sully2

    Sully2 Well-Known Member

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    I never have and never will. Even bought a lapping bar and the grit for it and after about 30 minutes stopped and thought hard on just what I was doing.

    Cleaned it all off...put the bar away where it will stay forever.
     

  3. cowboy

    cowboy Well-Known Member

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    What size is your lapping bar (1" or 30mm) and do you want to sell it?
     
  4. Sully2

    Sully2 Well-Known Member

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    1" and it would cost more to ship it than a new one costs ( approx)
     
  5. bruce_ventura

    bruce_ventura Well-Known Member

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    I install 5-10 scopes per month. I follow up with the customers after they live fire zero and shoot a few groups to see how the gun and scope are working. I install scopes on a wide variety of production and custom rifles. I also reinstall scopes on rifles that were exhibiting problems. I frequently see problems that resulted from using cheap rings, improperly installed bases, poorly aligned rings, not lapping rings, and not tightening ring screws to the proper torque values.

    For me, the primary objectives of lapping are 1) removing ring misalignment that leads to mechanical stress in the scope tube, 2) making the rings cylindrical to protect the parallax adjustment mechanism inside the forward tube, and 3) maximizing surface contact area to minimize ring marks and prevent scope slip.

    To do this, I don't believe that the surface finish needs to be completely removed by lapping. If the grit has only polished the finish, but not removed it down to bare metal, I still consider that area to be lapped. That's because the surface finish is non-compressible.

    I usually, but not always end up lapping the rings during a scope installation. I always confer with the customer before pulling out the lapping bar or reamer. Sometimes I conclude the benefits are not worth the effort. If the customer agrees with me, I won't do it. When I do lap, I might stop after the first inspection.

    For fully machined tactical rings - like Seekins, Near, Nightforce, etc., on a properly machined and installed rail, I don't usually expect lapping to be valuable. However, if I suspect a poor fit between the rail and receiver, which can cause the rail to bend and/or twist, I will lap the rings, even if they are fully machined tactical rings. I've found that most aluminum rings below a price point of about $75 are not fully machined, but rather have extruded ring surfaces. I always lap rings that have extruded ring surfaces.

    In your case I might have stopped lapping at your first photo. The lapping bar contact on your Seekins rings actually might have been uniform enough at that point in the process. It appears as though there were high spots on the leading and trailing edges of the rings when you started. However, I can't tell from the photo how much of the finish in the center area was polished by the grit. If the center area was at least 75% polished I would have stopped there.
     
  6. mtnwrunner

    mtnwrunner Well-Known Member

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    Bruce, do you lap both the tops and bottoms or just the bottom half of the rings.

    Randy
     
  7. Greyfox

    Greyfox Well-Known Member

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    I have never found the need to lap the high end tactical rings like Nightforce and Leupold Mk4's. I have lapped rings like the aluminum Talleys, and other lower priced rings. I found that 70% lapping to bare metal on the bottom half is sufficient. iMO.
     
  8. MOOSE39465

    MOOSE39465 Well-Known Member

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    Thanks for the reply Bruce. After taking picture I lap another 15 minute before I made contact with finish in center of Ring. I did notice when torquing down screws there was no movement in scope which is another plus.
     
  9. bruce_ventura

    bruce_ventura Well-Known Member

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    I lap both the saddle and cap, partly because I want the cap to be as cylindrical as possible, and partly because it's easier to get a good lap on the saddles when the caps are holding the lapping bar down on both rings. When I use a reamer, the caps must be in place.