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To lap or not to lop that is the ?

 
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Old 07-19-2013, 09:36 AM
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Re: To lap or not to lop that is the ?

I would lap those Talley rings for two reasons. First, the Talley rings that Iíve used looked like the ring surfaces were extruded, not machined. I could clearly see the extrusion marks. When I lapped them I could see that they were not perfectly round. Hereís a photo of a pair of Talley rings half way through the lapping process. Theyíre mounted on a Weatherby MkV. These rings needed to be lapped quite a bit to make the surfaces round. They were aligned fairly well before I started, too.
To lap or not to lop that is the ?-ring-lapping-3-_smc.jpg

This eccentricity in the rings reduces the surface contact area, or stresses and deforms the scope tube, or both. It can cause the scope to slip, the point of aim to change with temperature, and leave ring marks on the tube. So, to answer the OP's first question, I always lap Talley lightweight rings.

Second, Swaro Z5 scopes have a parallax adjustment knob on the turret housing that moves a focus lens back and forth inside the scope tube just in front of the turret housing. Thatís right where the front ring grabs the tube. You can see the sliding inner lens tube if you look into the objective with a small light. The sliding inner tube must fit precisely inside the scope tube, or else the focus knob will be stiff, the inner tube will bind, or the point of aim will not hold.

If the front ring is not round, it will deform the scope tube, which can put stress on the sliding lens tube. Now add the effect of shock and recoil. Over time, the parallax adjustment could become worn at the stress points, causing the lens tube to become loose. That could lead to a point of impact that changes with temperature or focus setting, or shot to shot.

Some of these problems can take a while to become noticeable. All of this can be avoided by lapping the rings.
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  #9  
Old 07-19-2013, 10:40 AM
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Re: To lap or not to lop that is the ?

Quote:
Originally Posted by bruce_ventura View Post
I would lap those Talley rings for two reasons. First, the Talley rings that I’ve used looked like the ring surfaces were extruded, not machined. I could clearly see the extrusion marks. When I lapped them I could see that they were not perfectly round. Here’s a photo of a pair of Talley rings half way through the lapping process. They’re mounted on a Weatherby MkV. These rings needed to be lapped quite a bit to make the surfaces round. They were aligned fairly well before I started, too.

This eccentricity in the rings reduces the surface contact area, or stresses and deforms the scope tube, or both. It can cause the scope to slip, the point of aim to change with temperature, and leave ring marks on the tube. So, to answer the OP's first question, I always lap Talley lightweight rings.

Second, Swaro Z5 scopes have a parallax adjustment knob on the turret housing that moves a focus lens back and forth inside the scope tube just in front of the turret housing. That’s right where the front ring grabs the tube. You can see the sliding inner lens tube if you look into the objective with a small light. The sliding inner tube must fit precisely inside the scope tube, or else the focus knob will be stiff, the inner tube will bind, or the point of aim will not hold.

If the front ring is not round, it will deform the scope tube, which can put stress on the sliding lens tube. Now add the effect of shock and recoil. Over time, the parallax adjustment could become worn at the stress points, causing the lens tube to become loose. That could lead to a point of impact that changes with temperature or focus setting, or shot to shot.

Some of these problems can take a while to become noticeable. All of this can be avoided by lapping the rings.

There is no such "requirement" for rings to be "round" on their ID. They can be very oval in shape and still grip the tube of the scope sufficient enough to prevent slippage....thats not to say that "oval" shaped rings WILL do the job.....but they can be out of round and still do as percieved.

One major scope manufacturer states to NOT lap their brand of rings.

Tell ya what makes rings go oval and scrape scope tubes....and thats trying to tighten down ring screws to about 50 FOOT POUNDS instead of what they are supposed to be....and then scratching your head when things go haywire
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