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Leupold Mark 4 problems

 
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  #1  
Old 12-01-2010, 10:58 PM
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Leupold Mark 4 problems

I have been asked to do some load developement work on a 7mm RUM that has been fitted out with a new Leupold Mark 4 6.5-20x50mm LR/T M1 rifle scope.

Now problems first started to show up when I zeroed in the rifle at 100 yards.

I got the scope zeroed onto the aiming mark then loosened off the turret grub screw and set the elevation turret to zero. I then tightened the grub screw.

First problem is that the turret is now very hard to rotate unless I back off the tension on the grub screw.

Second problem is that when I back off the tension on the grub screw the point of aim changes. This I found strange.

I held the rifle steady and looked through the scope as I loosened and tightened the grub screw. As I did this the cross hair moved about 3" at 100 yards on the target.

What am I doing wrong? Is the scope faulty? It is suppose to be a new scope.
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  #2  
Old 12-02-2010, 09:39 PM
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Re: Leupold Mark 4 problems

Does the rifle have a base with built in MOA? Are the rings set properly?

Sounds like the evelation on the scope is bottomed out and when the turret screw is loose it allows the erector spring to bounce a bit on the erector assembly. Eventhough you can turn the turret, it does not mean any more adjustments are being made. You need to determine if the scope is bottomed out .

Mark 4's generally have about 75 moa of travel built in. Since you have plenty of adjustment up, dial the evelation up until you feel the slightest bit of resistance not normal to previous turret travel. Loosen the grub screw and set it to zero. Now start dialing the turret down until you feel the same resistance keeping careful notice of the number of rotations of the turret. If it has 5 complete rotation plus or minus a few click in either direction, the optic is within spec to built in MOA travel.

Need to know more about the mounting system....
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  #3  
Old 12-04-2010, 06:31 AM
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Re: Leupold Mark 4 problems

Everything is fine with the mounts. Plenty of travel in both directions when the grub screw is just slightly tight.

But once you tighten the grub screw firm it is very hard in both directions and it definately has a POI shift on the erector tube.

Obviously there is something seriously wrong with this scope. Time to send it back for assesment.
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Old 12-04-2010, 08:45 AM
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Re: Leupold Mark 4 problems

Hopefully you aren't dealing with a counterfeit Mark 4. There are a lot of them floating around & from what I've heard, most don't know they are counterfeit until something goes wrong (many turret issues) & Leupold won't fix them.
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