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Gluv

Scope Calibration

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Does anybody on here go to the trouble of properly calibrating their scope turrets ? Or do most people assume because they have spent a good few quid that when they dial 1mil ,1 mil has gone on the gun ?

Im asking because I have noticed in the past a few people talking about fudging inputs to their ballistic programs to make them work

I am just in the process of making an off rifle jig to calibrate my scopes as we speak 

Gluv

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Sciope should be checked. Fudging anything  to fit 'data' is risky-you may fudge the wrong factor...price is at another distance,you will be out (let alone the issue of which inputsare actually accurate.Scope clicks are actually quite easy to check-by firing a few shots,before and after clicking-do the shots correspond to what should happen?

A very common errror is to fire say three shots at 600y,and guestimate the fall of those three shots...guestimate since shot four could well be inches out-solution ,fire ten shots-a decent sample,and caefully establish centre of group and use that as 600y drop.Inconvenient-well,if you don't do it properlly,every 'fudge adjusted' shot will tend to inconvenience/lack of correspodence (poor data in.poor information out).Do it right.

gbal

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I wouldn't have thought firing a group of shots would be accurate enough to be honest.  I would think getting a friend to accurately scribe a pen line whilst under directions from the man on the scope would be the way to go

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Brian Litz, THLR (and many others) recommend using a tall target test at 100m and shooting a number of groups while cranking in the elevation; 1MIL, 5MIL, 10MIL etc. Using a good tape measure to ensure both shooting distance and distance between aiming dots are spot on, and some maths, you can calculate whether there's any discrepancies in the scope.

 

You could also use a Horus chart to do the same thing, but getting the shooting distance accurately measured is key.

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That's more or less how they created the targets for the zeroing range at Bisley, so not really anything new, unless it's unknown

 

I knew a BR shooter many years ago (yes, can you believe that?!!!) and he came to the range once with us with a dial gauge contraption mounted to his scope to measure exact come-ups, as he didn't believe in accurate scope tracking back then. This was 20 years ago

Hopefully he's got better by now :lol:

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A different take on the Tall Target Test

 

Edited by TJC
Double posted. Apols.

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Hmm , see if you use fired shots to measure off you are introducing variables into the equation. If you just set your scope up level aiming at a fixed mark and then dial up full elevation whilst getting a friend to carefully cross the T on your plumb line , you could then very accurately measure what your real turret values are .

Gluv

Oh Lasers aren't really accurate enough , steel surveying tape is the order of the day for setting the distance....or a theodolite 👍

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Catch 22,thanks for posting the videos.

The Bryan LItz one  is quite excellent,and a model of clarity and explanation-while emphasising there has to be near zero tolerance for error of measurement.  Many rifles won't shoot as well as his-so perhaps more shots might help.The second scope tested shows just how some inaccuracy in tracking exists in some scopes (unless they are Night Force-but every scope has to be so checked).

   The TH blog,is as ever,scenic.It's key point is that the test seems "OK"- but because there is the considerable shooter error (about .4 moa) then the results are really not reliable enough to use.(I didn't follow the jotted notes eiher,but then writing 49.6=50.2 is always going to confuse,when precision is needed,unless some explanation is given).  Note Litz makes clear that a .003 correction is negligible,not that is zero-it's 1/3 click(which can't be done) in a 100 click up shooting solution...ie negligible.)

So,Bryan for how to do it properly,and Thomas for a salutory warning that human error needs attention-and most of us won't be immune.

Two points-check for the full range you will adjust your scope-ie  at least +30 moa if you are going to 1000y-any error may not be linear (ie scope might be relatively OK for 5,10 etc moa....but become less reliable for 20,25,30+  moa clicks. Just as for serious data on grouping,test thoroughly rather than assume and extrapolate from a small adjustment datum/sample.

   Oh,and it should be obvious-do all this in near perfect conditions,otherwise small errors will confound-you are going to rely on your scope findings evermore (though  regular testing is advisable) so they need to be accurate (minimal other factors error).

Gluv, I find -on bore sighting eg- it's very difficult indeed to keep the rifle scope absolutely steady while clicking in ( and there is no check possible).  Holes on paper have a considerable value,done carefully-though of course subject to some error (as Thomas shows) but not neccessarily much,as Bryan shows

Finally,note the laser point -a 1% error in measuring shooting range distance at around 100y,will seriously mess up your test results...Bryans 3 lasers didn't exactly agree. Maybe the steel tape is an investment-though it may shrink a very little in Thomas' Norwegian temperatures....   :-)

Be as careful as is possible with measurement,and assume nothing.         "Approximately"  won't do here.            

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For me the challenge is location to perform such calibration testing.

I don't have land to use for such testing and the only ranges I shoot on are MOD, who won't permit deviation from the usual 600/1000m targets on offer.

😞

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It's a mute point but I wonder how many people would sell their scopes if they found that tolerance was perhaps 3 to say 5% on a tracking repeatability test, something for which calibration tests are of little use.  I would be more inclined to check tracking repeatability V's calibration as the latter is something that I worry about only once I knew that tracking was repeatable.

 

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Catch22 (might be almost appropriate here!),but if you can only shoot these 'MOD 600/1000m targets,would you need to be much concerned about fine scope tracking...I don't quite know just what these targetsmight be,but if they show bullet holes it should be possible to shoot at some low point on them,then crank in 10/15 moa on scope and shoot again with same aim point,and note how much hiher the cranked shots impact?  Tricky at 600y though-but my first point comes in-does it matter if scope is a few inches out...won't that tend to  show anyhow?

    Maybe I've not quite got your set up,but the scope click test really is to check for rather small 'errors'-the scope is about 2-5% out, ie you thinkyou've diallled in 25 inches,but it's really 27 (or 24 etc) and that ballpark matters only for fairly fine precise  shooting...?  I would not be surprised i many cheaper (not rubbish cheap) scopes don't really click too accurately...but  at short range and fair size targets it won't be crittical.

     I like rifles/rigs that can hit  genuinely hit (sub) moa  reactive targes at ,say,750y,but I also shoot Fig 11s with rifles that are not that precise,but a target down is a target down....1/4 moa rig/scope/ammmo/me isn't mandatory. Stll,I know what you mean too-it's nice to know just what your rig is doing-but often it's bettr not to push that-it might disappoint in detail...my favourite fig 11 downer ,probably don't shoot 2 moa,let alone .2 moa,but the .2 ones  are simply not needed (for that fun).     :-)

"good enough' is often ...well.....good  enuff

 

 ( the lesson of the Ruger Mini 14....great fun,hardly precision,not even CSR  !)  :-)

gbal

 

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58 minutes ago, VarmLR said:

It's a mute point but I wonder how many people would sell their scopes if they found that tolerance was perhaps 3 to say 5% on a tracking repeatability test, something for which calibration tests are of little use.  I would be more inclined to check tracking repeatability V's calibration as the latter is something that I worry about only once I knew that tracking was repeatable.

 

Yep,reliability and validity. Does the measure repeat when the same ruler (etc) is applied to the same object?If not,only a small error is 'tolerable'.If it is 'reliable',then the issue of validity arises-is it indeed measuring what you want to measure.A very general distinction in measurement-if not repeatable,not much else is possible.

  So tracking repeatability in this context matters-and if repaeted clicks are reliable-same elevation,then you can ask-and is this reliable elevation exactly what I tink,or is it reliably a bit different. (10 moa for example,or really 10.2 moa)Of course you best know which,but reliability comes first-if it's lacking....you have a problem of a similar magnitude,prior to validity ....

    Litz' tracking pointis that if that is reliable,then if validity is out,it can be fixed with a % corrsction factor-derived fromyour test measurements..."My scope is 5% out -high or low_so 20 clicks theory  actually need 5% more (or less). Ie 21 or 19  clicks)"

But see the 'error'in context- a 5% might mean little (depends on target size eg) but it might advise a better scope.....just like all the other factors- tin can at 100 y does not need a Bench Rest precision-though that will be nice,and hit more,more centrally.

gbal

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11 minutes ago, gbal said:

Catch22 (might be almost appropriate here!),but if you can only shoot these 'MOD 600/1000m targets,would you need to be much concerned about fine scope tracking...I don't quite know just what these targetsmight be,but if they show bullet holes it should be possible to shoot at some low point on them,then crank in 10/15 moa on scope and shoot again with same aim point,and note how much hiher the cranked shots impact?  Tricky at 600y though-but my first point comes in-does it matter if scope is a few inches out...won't that tend to  show anyhow?

    Maybe I've not quite got your set up,but the scope click test really is to check for rather small 'errors'-the scope is about 2-5% out, ie you thinkyou've diallled in 25 inches,but it's really 27 (or 24 etc) and that ballpark matters only for fairly fine precise  shooting...?  I would not be surprised i many cheaper (not rubbish cheap) scopes don't really click too accurately...but  at short range and fair size targets it won't be crittical.

     I like rifles/rigs that can hit  genuinely hit (sub) moa  reactive targes at ,say,750y,but I also shoot Fig 11s with rifles that are not that precise,but a target down is a target down....1/4 moa rig/scope/ammmo/me isn't mandatory. Stll,I know what you mean too-it's nice to know just what your rig is doing-but often it's bettr not to push that-it might disappoint in detail...my favourite fig 11 downer ,probably don't shoot 2 moa,let alone .2 moa,but the .2 ones  are simply not needed (for that fun).     :-)

"good enough' is often ...well.....good  enuff

 

 ( the lesson of the Ruger Mini 14....great fun,hardly precision,not even CSR  !)  :-)

gbal

 

I guess it's all about trying to eliminate the variables. If you are shooting over a 1000m and youre ballistic program says put e.g. 10 mil on the scope ,but because you're turrets aren't exactly .1 per click  you are only putting 9.5mil on , then you're going to miss .

Im making an adjustable heavy steel jig with a picatinny rail on top that will allow me to level the scope and clamp it up with zero movement.This will allow me to do very accurate tracking tests and to work out exactly what every turret click is worth. I can then put that turret value into the ballistic computer.

Its all about the small refinements 🙂

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Using ballistic calculators such as Trasol, you can input the actual scope calibration. Though it's limited to a 'general' change in calibration, not margins of calibration error at different elevation/windage settings; etc 0 to 10MILS is 0.1MIL error, but 10 to 15MILS is 0.3MIL error.

btw, I use both Trasol & Lapua's 6DOF and find them to be excellent- their calculations appear to be very close based on identical equipment, load and environmental data inputs.

@gbal

i understand your point about fixed point shooting, though many of the MOD ranges near me offer a variety of targets at odd ranges. Sennybridge F range for example has various targets out to 1200m, none of them at fixed intervals. But yes, it's not like I'm out stalking/varminting. However I would like to know my scopes margin of error, either as evidence for a repair under warranty or to understand the issue and adapt/adjust my drop tables to make the best of it.

Plus I'm just bloody nosey and like to geek out on occasion 🤓

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7 hours ago, gbal said:

Catch22 (might be almost appropriate here!),but if you can only shoot these 'MOD 600/1000m targets,would you need to be much concerned about fine scope tracking...I don't quite know just what these targetsmight be,but if they show bullet holes it should be possible to shoot at some low point on them,then crank in 10/15 moa on scope and shoot again with same aim point,and note how much hiher the cranked shots impact?  Tricky at 600y though-but my first point comes in-does it matter if scope is a few inches out...won't that tend to  show anyhow?

    Maybe I've not quite got your set up,but the scope click test really is to check for rather small 'errors'-the scope is about 2-5% out, ie you thinkyou've diallled in 25 inches,but it's really 27 (or 24 etc) and that ballpark matters only for fairly fine precise  shooting...?  I would not be surprised i many cheaper (not rubbish cheap) scopes don't really click too accurately...but  at short range and fair size targets it won't be crittical.

     I like rifles/rigs that can hit  genuinely hit (sub) moa  reactive targes at ,say,750y,but I also shoot Fig 11s with rifles that are not that precise,but a target down is a target down....1/4 moa rig/scope/ammmo/me isn't mandatory. Stll,I know what you mean too-it's nice to know just what your rig is doing-but often it's bettr not to push that-it might disappoint in detail...my favourite fig 11 downer ,probably don't shoot 2 moa,let alone .2 moa,but the .2 ones  are simply not needed (for that fun).     :-)

"good enough' is often ...well.....good  enuff

 

 ( the lesson of the Ruger Mini 14....great fun,hardly precision,not even CSR  !)  :-)

gbal

 

 

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Gluv, an easy and fairly cheap solution Is to buy an optical colimator. In essence it looks like grid lines in front of the reticule, you can vary the size of the grid with your scope magnification. It allows you to accurately “see” what the turret adjustments are doing and accurately measure them. In an extreme case I have seen vertical adjustment also give a degree of horizontal displacement ( I could see the crosshairs “jump” when manipulating the turrets). It is also required to have the vertical crosshair perfectly vertical  to avoid horizontal displacement which will affect vertical displacement also - vector.

The advantages of using a colimator are that you see what you tracking is doing - at home and it isolates just that and it is easy to check the full range of vertical and horizontal  tracking adjustment Things that it  does not do -!show the effects of recoil on scope tracking.

With other forms of establishing how your scope is tracking you get into many external factors including  - rifle cant, load variations and to a lesser extent mechanical tolerance variations within the scope due to things like temperature change.

 

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and if you are going to great lengths to test our scopes to ensure there isn't a disastrous 2% error what are you doing to test your ballistic app to ensure its output is equally valid ????

i get the point and i do it too but this game is a chain. if the scope is accurate to 0.001%, your rifle shoots 0.001moa your runout is 0.25 thou but your app data is pish your results will be, well, equally pish

and really the only way you are going to be sure your 9.5 mil is reliable at 1500m is if you have dope to there or beyond. So to get a complete solution we end up shooting groups at range. At least in the UKD world. Can't avoid the shooter...

like reloading, there are diminishing returns.  gbal's point really, worth it if the result requires it.

still, I enjoy reading the results so please keep us informed.

I think Lowlight uses a scope testing rig like the one described above to test students scopes on his classes. On the basis of those tests Kahles are a bargain, if they float yer boat

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There is of course a short cut for some of us, insofar as many scopes that we use have already been tested (using Horus calibration targets).  See the "Mechanical Precision Test" section in this article:

http://precisionrifleblog.com/2014/08/13/tactical-scopes-mechanical-performance-part-1/

 

best-scopes-reviews1.png

 

My own scopes, luckily seem to have fared very well, with perfect scores on 1st and half a click on 2nd adjustments which is as far as I adjust them anyway (ie max 15 MRads).  I haven't tried mine out against a tall target but may do out of interest to see if I get the same result sometime.

 

The big shocker from the test above seems to be the March scope. That may well be down to a faulty scope as it's hard to believe any precision scope would do so badly!

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55 minutes ago, VarmLR said:

There is of course a short cut for some of us, insofar as many scopes that we use have already been tested (using Horus calibration targets).  See the "Mechanical Precision Test" section in this article:

http://precisionrifleblog.com/2014/08/13/tactical-scopes-mechanical-performance-part-1/

 

best-scopes-reviews1.png

 

My own scopes, luckily seem to have fared very well, with perfect scores on 1st and half a click on 2nd adjustments which is as far as I adjust them anyway (ie max 15 MRads).  I haven't tried mine out against a tall target but may do out of interest to see if I get the same result sometime.

 

The big shocker from the test above seems to be the March scope. That may well be down to a faulty scope as it's hard to believe any precision scope would do so badly!

Only thing is those results only count for those individual scopes tested. Just because one scope from Khales passes doesn't mean the rest of the batch will 🤔

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It doesn't actually matter if your scope is off even by 10%. All can be allowed for in your ballistic program .What matters is that all adjustments are repeatable and consistent 

Rubbish in = Rubbish out 👍

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Gluv, if only it was that  relatively easy always....you are right about N=1 sample on scopes (both for a poor and good performance)-test more (a one shot group is unconvincing,a two shot gropu a little less so-but when someone  shoots 5x5x5 shot competition winning aggregates,luck etc seems an increasingly improbale explanation!. 

Meanwhile-by no means all ballistic engines will allow a non linear compensation to be 'automatically' applied (simple case is with BC-Sierra help with three differnt values for velocity bands,but not all ballistic solvers will allow that inputs. err...those inputs...  :so too bad if your bullet flight crosses bands-as it will-there are infinite bands,not just three!).  :-)

More computing power will cope better...but then input data will need to be 'more' too,and more accurate  (fit like a Gluv?)

AS I said in an earlier post,without reliability (same thing gives same result) you are doomed,but non linear variation gets complex....shooting is not stochastic,but it is complex... Fortunately targets are not infinitely small..... :-).... And generally good (enough) compensation cn   be applied to give a decent shooting solution...barn doors are not safe - that said,always 'scope' for improvement- even if N = 2 plus shots are allowed !

gbal

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1 hour ago, Gluv said:

Only thing is those results only count for those individual scopes tested. Just because one scope from Khales passes doesn't mean the rest of the batch will 🤔

Hmmmm...I'd like to think that at the top tier, QC was better than that Gluv but I honestly wouldn't know.  The feedback to the author of that test suggests that many of the scopes on there when individually tested by owners did match quite closely, which is what you might expect given the same design, construction and quality control applied in manufacture.  Not always the case of course, but if nothing else it may be a reasonable indicator of the ballpark for the scopes listed. 

No app can account for large variations in repeatability though.  3% out on repeat tracking tests wont have much relation to a particular scope performing as designed (calibrated), ie if the scope was designed to deliver 60moa total travel but in fact delivers 59.5moa (1% calibration error) by design, that counts for little if it can't repeat that tracking every time.  The calibration from the factory and turret design may be true to within 1% but entering that into your app isn't much good if on one pass, it matches the 1% and on the next swings to 3% for the same test and so-on, hence repeatability has to be the more important gauge because any calibration error can be compensated for. Lack of repeatability cannot.

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VarmLR, with reference to that article. It is now several years old and some of the scopes have evolved. With reference to the March scope on that test I remember asking March Optics- they told me that the scope sent for that test was a test model and for whatever reason I forget had a different system of milradian in it  - there being 6000or 6300 or 6400 degrees in a circle, depends which criteria you use, as a miltadian is an angular not linear measurement.

 

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20 minutes ago, VarmLR said:

Hmmmm...I'd like to think that at the top tier, QC was better than that Gluv but I honestly wouldn't know.  The feedback to the author of that test suggests that many of the scopes on there when individually tested by owners did match quite closely, which is what you might expect given the same design, construction and quality control applied in manufacture.  Not always the case of course, but if nothing else it may be a reasonable indicator of the ballpark for the scopes listed. 

No app can account for large variations in repeatability though.  3% out on repeat tracking tests wont have much relation to a particular scope performing as designed (calibrated), ie if the scope was designed to deliver 60moa total travel but in fact delivers 59.5moa (1% calibration error) by design, that counts for little if it can't repeat that tracking every time.  The calibration from the factory and turret design may be true to within 1% but entering that into your app isn't much good if on one pass, it matches the 1% and on the next swings to 3% for the same test and so-on, hence repeatability has to be the more important gauge because any calibration error can be compensated for. Lack of repeatability cannot.

All quality control allows for a certain amount of tolerance in manufacture . The high end scopes generally just have the tighter tolerances.

Perfection every time does not exist 🙂

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