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Turret backlash??

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/12/2009 at 09:12
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Hi, A number of years ago I purchased Leupold Vari X-III 6.5-20's from Premier Reticles that was modified by them in respect to a power boost and the reticles. Anyway they sent their own instructions with the scopes. I'll quote this one statement; " A hint to improve the accuracy of the adjustments is any time a counter-clockwise adjustment is made to always go beyound your new setting by 1-2 minutes and then come back to it in a clockwise direction. This procedure will eliminate any backlash in the adjustment assembly". My question to you is this still necessary today with a scope like the Nikon Tactical 2.5-10 or even the scope Weaver just discontinued Classic Extreme illuminated riticle 2.5x10x50mm & 56mm scopes? Also can following the above procedure have an adverse effect on the desired point of impact with any of todays higher end scopes?
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/12/2009 at 09:32
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I do this as a matter of habit, but not only in counter-clockwise adjustments. I cannot see that it could have any adverse effect.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/12/2009 at 09:47
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Have quite a few Leos with side AO's and have never had the dreaded leo backlash problem. Personally I llike to start at infinity with a side AO and dial back anyway as it gives a really good idea of the size, location, and speed of the mirage.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/12/2009 at 10:05
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Originally posted by Dale Clifford Dale Clifford wrote:

Have quite a few Leos with side AO's and have never had the dreaded leo backlash problem. Personally I llike to start at infinity with a side AO and dial back anyway as it gives a really good idea of the size, location, and speed of the mirage.
Thanks Dale, but I should have made my question more clear. I'm asking more specifically about the elevation & windage adjustments. And this instruction sheet sent to me by Premier Reticles was also referring to elevation & windage. Back in those days Leupold did not have the side parallax on the Vari X-III scopes.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/12/2009 at 12:36
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oh that type of backlash, it used to called a rubber mallet, or a screw driver handle whack. personally if I had to do that with a scope I would get rid of it --especially a tactical. None of the tacticals (or regulars) that I use need this extra step.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/12/2009 at 20:54
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    fourinone:  I think it's a good idea to go past and then back to load the adjustments. Another thing that I've found helpful for reliable tracking is to periodically run the w/e adjusters to both ends of their travel and then back to your zero.  

Edited by Al Nyhus - October/13/2009 at 04:59
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/13/2009 at 07:49
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Originally posted by Dale Clifford Dale Clifford wrote:

Have quite a few Leos with side AO's and have never had the dreaded leo backlash problem. Personally I llike to start at infinity with a side AO and dial back anyway as it gives a really good idea of the size, location, and speed of the mirage.
 
Dale,
I have a Leo, and that gives backlash problems on the AO, or put differently, seem to loose focus.
Interesting observation you made about playing with the focus in order to pick up mirage.
 
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/13/2009 at 09:52
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Sometimes running the elevation totally out and leaving it for a couple of days is a good way to find out how bad the scope really is, --if you do a lot of long range shooting with the scope you are using at least 2 revolutions all day long, (unless using an Erek or IOR mil). Most rifle/load combinations aren't going to see differences in a couple of clicks, even if the shooter could tell the difference. I believe Mr. Nyhus shoots ultra high end bench guns off of solid rests and coupled with his skills hysteresis could show up. In action shooting matchs with time pressure this isn't an option.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/13/2009 at 09:54
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Originally posted by Al Nyhus Al Nyhus wrote:

    fourinone:  I think it's a good idea to go past and then back to load the adjustments. Another thing that I've found helpful for reliable tracking is to periodically run the w/e adjusters to both ends of their travel and then back to your zero.  
 Well the more I think about it, the more I feel it has to do more good than bad. There are tolerances in all machined parts, and therefore it stands to reason there would be some amount of "PLAY" when changing direction with the turrets. Thanks for each of yours input.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/13/2009 at 10:11
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stands to reason there would be some amount of "PLAY" when changing direction
not a question of good or bad--- any play in the mechansim is off set by 10 times the amount of play in the shooter.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/13/2009 at 14:04
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Originally posted by Dale Clifford Dale Clifford wrote:

stands to reason there would be some amount of "PLAY" when changing direction
not a question of good or bad--- any play in the mechansim is off set by 10 times the amount of play in the shooter.
I agree with the human factor, It's hard to tell how many times a scope gets blamed for a flier that was due to the shooter. I have even second guessed my scopes when making adjustments in windage and or elevation and not get the intended result with the next shot. This is one of the reasons why I asked this question to begin with. I wanted to zero a hunting rifle for a max point blank range with a new scope and mount system and me shooting. All sorts of questions come to mind in this process when a flier occurs. So if nothing else, it can help with the process of elimination. I guess if the shooter is off by .001" in the way he or she aims at a target that can be how far off at 100 yards? There's 3,600 inches in 100 yards. Would that be 3.6 inches??
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/13/2009 at 14:17
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I don't think it works like that with the being off by .001" in aim thing....
 
Your aim isn't the same as the other stuff you are thinking about.
 
Only way would be if you was using iron sights and you always used them incorrectly but consistently....say putting the 10" target circle on top of the post at each range of 200, 300, or 500....then you will have differing amounts of bad aiming.
 
EDIT -  Actually that would be the same off-aiming as well....it's pretty hard to goof up aiming to a large degree without intentionally doing it.  You would need to be using the middle of the post in the above scenario...with the top of the post being the correct spot for bullet placement.  If you sight in with the same part of your sight or reticle and continue to use it you are good regardless.


Edited by danjojoUSMC - October/13/2009 at 14:29
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/13/2009 at 14:45
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I agree there will always be a human factor but it should be to a lesser extent at the times where most people will be using the turrets (medium to long range from a solid rest or prone).  In such a situation, any decent shooter with a fairly accurate rifle certainly would notice (or be messed up by) the adjustment being a couple of clicks off.

With many scopes going past your intended adjustment and coming back is necessary to ensure it isn't being "lazy," but if you do much shooting at extended distances this gets really old.  And that's the last thing you want to have to remember to do when a shot really counts (be it hunting or competition or whatever).  So naturally I advise for that type of use if you find your scope doing that, replace it with one that doesn't.   Of course if you won't mess with the turrets much after zeroing, or only do on a more casual/occasional basis, it may not be that big a deal to you.

None of the higher level tactical scopes I've used have needed this technique and even some cheap non-tactical ones haven't seemed to need it.  The problem is knowing--you can test for it and find an obvious problem, but if a scope only "sticks" 1/10th of the time, the only way you'll likely discover that is through a lot of use.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/13/2009 at 17:20
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Originally posted by danjojoUSMC danjojoUSMC wrote:

I don't think it works like that with the being off by .001" in aim thing....
 
Your aim isn't the same as the other stuff you are thinking about.
 
Only way would be if you was using iron sights and you always used them incorrectly but consistently....say putting the 10" target circle on top of the post at each range of 200, 300, or 500....then you will have differing amounts of bad aiming.
 
EDIT -  Actually that would be the same off-aiming as well....it's pretty hard to goof up aiming to a large degree without intentionally doing it.  You would need to be using the middle of the post in the above scenario...with the top of the post being the correct spot for bullet placement.  If you sight in with the same part of your sight or reticle and continue to use it you are good regardless.
I was not sure about my way of figuring this, that is the main reason I ended it with the question mark. It seems those 10,20,30moa bases were something like .001" for each moa gain?? I can't remember for sure. Someone here knows this off the top of their head and I did too at one time or another. But I think that when making an adjustment the gun is not likely to rest in your bag the exact same way to aim at the same target you just shot at prior to the adjustment. So I'm not sure what effect this could also have in not getting the expected point of impact change?
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/13/2009 at 20:01
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    My periodic running of the w/e adjustments to their travel limits and then back to 'zero' is obviously not done in a hunting or competition scenario. Wink
 
     Testing is one thing.....competition when the timer is running is another. Smile  -Al
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/16/2009 at 11:14
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Just an update on the subject. I have a friend who is one of the best machinist in the country and was involved with a very respected tactical scope manufacture who has their own line of tactical scopes now. Anyway he said in a scope with internal windage & elevation adjustments, backlash is unavoidable because threads have to be able to move when you turn them, so there is at least enough clearance for them to turn. As a result you will have backlash. He did say that this company recommends turning past the setting and then go back to the desired setting.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/16/2009 at 12:23
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yes-- but does he ever shoot?
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/16/2009 at 13:21
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While the threads do need enough clearance to turn, adequate spring pressure on the erector "takes out the slack"  such that it should not be an issue.   The end result for a scope with this problem, is the erector being in two different locations for the same turret setting depending upon if you went past the mark and came back or not.  The interface between the two and obviously the spring pressure that holds them together is not up to the task.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/16/2009 at 14:40
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Well put Jon--- I was thinking something like hysteresis is a non-deterministic system usually of at least 3rd order (the hysteresis loop), involving at least two attractors in which the system will return to basin of attraction unless pushed out by an outside force and if done rapidly enough will oscillate. Systems,mechanical and electrical engineers try to linerize the problem to make the system as deterministic as possible by removing the small time interval components associated with the system. (linear time invariant). Two non-deterministic systems (the shooter and a scope) working in harmony is a difficult goal.  Would the amt. of error taken out by overshoot then back be off-set each time by a correct sight picture on the part of the shooter? Not likely. Is the statistical bell-curve for the error produced by the backlash within the sighting error of the shooter. Most likely. (especially in good expensive scopes). I would really like to know the name of that scope maker.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/17/2009 at 07:30
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      It's worth noting that manufacturers of high end, precision measuring tools recommend periodic stop-to-stop travel of the instruments be done to avoid the mechanical lag that happens when a system with a range of adjustment is operated within a relatively narrow window of it's total range for an extended time.
 
    $19.95 micrometers need not apply. Wink
    
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/18/2009 at 05:38
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Do other scopes in similar or higher price range have the side focus lash issue as (at least some) Leupolds have?
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/18/2009 at 07:45
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Originally posted by puppezed puppezed wrote:

Do other scopes in similar or higher price range have the side focus lash issue as (at least some) Leupolds have?
 
    A Nightforce NSX 5.5-22X56 I worked with recently had a tiny bit of 'lag' in the a.o. if I turned it 'out' from where I had it set. If I went past and then came back...all was well.
 
   A new Leupold Competition Series 45X shows no a.o. lag going either direction.
 
   A Nikon side focus a.o. on one of my guns is fine going either way.
 
   I really think it's individual to each scope, not to a manufacturer.
 
   Admittedly a small sample as I'm not a big side focus a.o. user.
 
    Good shootin'.   -Al
 
 
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/18/2009 at 08:58
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Sorry for being away from my computer a couple days. I did at the time question this man about spring presure correcting for the screw tolerance. I can't remember exactly what he said being he talks over my head. But I remember him saying that it would not take out the backlash. I think it has something to do with the threads being loaded on one side of the "V" "thread" in one direction of rotation verses being loaded on the other side of the "V" "thread"in the other direction. I recall him mentioning seeing a video on these scopes from the manufacture and he did see the person in the video turning past and then turning to. I'll have to question about how to see this video. I do feel that it is only necessary to do in one direction. Like you should always finish up in a clockwise direction. So if you have to make another adjustment that happened to be clockwise, it would not be recommended to go past and then return counterclockwise, that would defeat the purpose. As for the name of this company....I may call them myself and ask them point blank this question before I go on record and speak on their behalf. This friend of mine told me that the threads in a high quality CNC lathe or mill will have a ball thread rather than the normal "V" thread. The ball thread makes it possible for near zero backlash but still a measureable amount with the right measuring instruments.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/18/2009 at 13:48
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NF threads run 110 threads per inch , and consider 1/30 the thickness of a human hair too much backlash, can a human align a target and crosshair this fine?? Like to see it.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/18/2009 at 20:10
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Originally posted by Dale Clifford Dale Clifford wrote:

NF threads run 110 threads per inch , and consider 1/30 the thickness of a human hair too much backlash, can a human align a target and crosshair this fine?? Like to see it.
I went into this whole thing as a question that I don't really know the answer to. And I appreciate your's and all responces, I kind of get hung up on something sometimes and can't make myself settle until I'm throughly convinced. But one thing I have not come to the conclusion of is that this is "too much backlash." I so far have concluded that the backlash will not be the same from one scope to the next even if both are the same exact model number. The machined parts can vary from one run to the next and there's the possibility of the tolerances of the mating parts being a more loose fit compared to what may sometimes be a tight fit. And of course there is normal wear from the use that one scope may get more than another. Another thing to consider is that it may not be just the thread itself that may be affected here in this situation, I realize that the spring takes care of most of what may be an issue. But, I don't know yet, there maybe other parts of the assembly that may not settle in the same fashion being pushed down verses being let up??? Thanks again for your time in this matter.

Edited by fourinone - October/18/2009 at 20:13
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