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Alignment Bars - Acceptable Variance

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/17/2012 at 07:17
puffadder View Drop Down
Optics GrassHopper
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Question...What is an "Acceptable" variance when using Scope Alignment bars? Or imust it be perfect?I am mounting a 30mm tube on a Sako with Talley Quick Detatch Rings and Mounts. Talley has already sent me (free of charge) another set of bases. I got the same result. The rear alignment bar is about .015" to .020" higher. I posted a similar question on the Rifle Scope Forum the other day and got some great advise...wanted to see if any varianse is OK? Thanks
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/17/2012 at 08:49
Thundey View Drop Down
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Have you measured the receiver on the rifle yet to see if its the problem?  I read your thread in the other section, and not sure if that has been done yet.  Sounds to me like it is likely the issue.

Personally that is too much difference between the two for my liking, although it probably wouldn't cause any issues.  I know it was already suggested but the burris sig rings would fix this issue, and ensure 100% absolute concentric mounting of the scope.  Or you can lap the rings you have, Supertool is usually really good with helpful information, but I'll respectfully disagree with him on lapping rings.  It won't or shouldn't require so much lapping that you won't get the proper scope to ring fit. And actually should improve the grip provided by the rings.

lapping rings

Hope this helps.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/17/2012 at 09:26
puffadder View Drop Down
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Thanks, Thundy...the more replies I get the more I'm thinking that it is the reciever (although, I don't want to believe that) How would you measure the receiver?? The Burris Rings have the same insert as the Sako OptiLock Rings...and will work, I'm sure. Maybe I'll lap the Talley's that I have...doubt if I can return them anyway.....thanks again for your comments
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/17/2012 at 10:39
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This is a post i remembered that glen seekins posted once. On top of what he says lapping will most just take material off the bottom half of the ring. So now your ring is not round anymore

Quote I don't own a lapping bar anymore if that helps your decision. Im not going to recommend either way because there is always an exception and sometimes things happen. your mileage may vary

Rings being in line "perfectly" will never happen, even if you lap them unless you have a machine lap/ream them and they start considerably undersized. The pressure and stroke you put on the lapping bar will take away material un evenly. Lapping makes the rings larger by some amount so your scope tube will have LESS contact because the rings are now grossly large. The rings are made .003" larger than your scope tube. If you lapp the anodizing off, that's .002" per surface so .004 more diameter.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/17/2012 at 11:00
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You can have perfectly aligned rings, if you use a bottom and top style ring, remove material from the bottom half, and epoxy-bed the scope itself to the bottom of the ring.  The top half of the ring should self-level on the bedded bottom half.  Everything will be perfectly aligned and 100% contact.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/17/2012 at 11:30
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Bed the rings, a novel idea. Never thought of that. Would that not require removing even more material to allow more for more bedding material?  Still seems a viable option.  Excellent
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/17/2012 at 11:55
Bitterroot Bulls View Drop Down
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Just takes a few mils. I bedded some Leupy PRWs on my Model 7. I was going to adjust the mounting for eye relief on that rifle. Would a pic be of use?
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/17/2012 at 12:18
Thundey View Drop Down
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If lapping is done correctly it should remove material from the top of the ring as well. Or you are doing it wrong!  I will also respectfully disagree that they will have less contact because they are "grossly large"  The contact area grows vastly larger the more concentric the ring and scope are with each other(to an extent).  I then use a piece of black electricians tape over the bottom half of the rings, trim it with a razor so that it sits flush.  Never had a scope move, slide, get scraped, dented, or any other plethora of problems.  I guess you could always think of it like this, is it better to have 150 inch pounds per sq inch of pressure spread over an area of .3 inches squared, or have 45 pounds of pressure spread out over 1.2 inches squared.

There is also epoxy bedding the rings as BitterRoot Bulls suggested, which is a good idea.

If lapping is done incorrectly you do run the risk of making a mess, avoid using the lapping bar on the bottom ring only, avoid using the lapping bar if it will take longer than 5 minutes to get the desired results. Don't lap only the bottom of the rings. Why you are instructed to install the tops and lightly torque them down.  Don't press down or pull up on the lapping bar, only slide it back and forth inthe rings, or you run the risk of removing more material in certain areas making an oblong shape, in other words be gentle.

I think a pic would be great BitterRoot!
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/17/2012 at 13:30
Bitterroot Bulls View Drop Down
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I have lapped a bunch of rings.  It is easy to get it wrong, even if you are careful.  It is also easy to take too much material.  It is also possible to just lap the bottoms and get good contact.  The tolerances in the ring screw holes allow for the tops to settle onto the scope surface.  this is also why you can bed just the bottoms.
 
I generally don't do anything to rings on a bedded rail, as they should line up perfectly, and are machined to tight tolerances.  I bedded the PRWs I mentioned because I had lapped them on a two base setup, and needed to get them back to square for the rail I put them on.  It worked very well, and provides excellent contact.
 
The electric tape should give you good contact, but it also naturally has some give during recoil, which could be a problem.
 
I just stole the ring bedding from the benchrest guys.  They have been doing it for years.  If I have a contact issue, it is my preferred fix.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/17/2012 at 18:01
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How can it not take more off the bottom?  Gravity alone will cause that.  Those bars are heavy, and push down under their own weight.  So more is going to come off the bottom.  IF you tighten down the caps to much then the bar will not move.  The only way it could not is if you some how was able to pull up at just the right amount of pressure to make it even.

Plus you are pulling and pushing from one end of the bar, that is going to make it dig slightly into that ring more.  Lapping is just a bad idea all the way around.  

That is what Glen was talking about with using a machine to do it.  It allows you to take out all these variables.  Personally I will trust Glen on this.  He is a master machinist and knows more about this kind of stuff than most of us will ever dream of. 

Lapping is a bandaid to a bigger problem.  It does not fix the problem.

I used to lap rings as well.  Then I saw the light.  Once you lap them they are pretty much dedicated to a specific rifle.  Unless you do what Matt did and bed them back square which would be a PITA.  If you fix the problem then you don't have to lap them to begin with and they fit on any rifle. 

There is just no need to lap them if you fix the problems properly.  That is what Glen was talking about as well, he doesn't own a lapping bar any more because he fixes the problem properly. 

There is a reason why most manufacturers void the warranty if they are lapped.


Edited by supertool73 - March/17/2012 at 18:11
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/17/2012 at 18:25
Bitterroot Bulls View Drop Down
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ST, I agree.

I don't lap anymore.  There is no need as long as your base is square and true.  There can be a need if you use two piece bases, and there is a problem with the action hole spacing/alignment.  In that case (which is pretty often) you can use some sort of jig to get the bases square to each other, and bed them square (TPS sells/sold a jig for doing that), or (preferably) bed a one piece base, or bed the rings.
 
Here are the pics:
 
 
 
Of course these rings are for THIS scope now.
 
 
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/18/2012 at 08:32
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What about lapping vertically split rings (like the Talley's) in the original post? Still seems like an endeavor in futility to me. 
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