Scope testing and mounting for precision shooting

[Tim K]

When I first go into the long range game, I started with a Leupy MK4. I could tell the reticle was canted, and that got me wondering what else might be wrong with it. In order to do some testing, I made jigs and test targets and developed a little test protocol. Since having the scope level on the rifle is so critical, part of the protocol involves getting the scope mounted in the rings so it is dead level when mounted to the rifle.

I just bought another NF and also have a USO that showed up a few months ago. Yesterday I decided to drag out all the stuff and test both scopes.

The test target is two sided. I used my CNC router to very precisely scribe lines representing MOA hash marks at 100 yards (1.047" apart). The other side is scribed with mil rads.

http://i27.photobucket.com/albums/c173/tkulin/CIMG5346_zps4a3e0a5c.jpg

The target got hung perfectly plumb out in the yard at a range of precisely 50 yards. I can get to 100 yards, but it involves the scope being outside while testing and it was cold up here yesterday.

http://i27.photobucket.com/albums/c173/tkulin/CIMG5348_zps4df3016f.jpg

Here's a view from the test position.

http://i27.photobucket.com/albums/c173/tkulin/CIMG5349_zps73e716fe.jpg

This is my test jig. The first step is to get it level and pointed at the target. I check it with both the carpenters level shown and a machinist's level.

http://i27.photobucket.com/albums/c173/tkulin/CIMG5357_zpscd55193c.jpg

Next, I install the scope on the rail section and aim it all precisely at the test target. At this time, I level the reticle by lining it up with the vertical line on the test target.

http://i27.photobucket.com/albums/c173/tkulin/CIMG5356_zps0be1cb5e.jpg

Once I have the scope level, I proceed to the actual testing. The fixture is extremely rigid, so I can crank away on the knobs without fear that the scope is moving. After cranking the knobs around, I do the following tests.

Box test - confirms the scope returns to zero.
Click value test - measure how much the reticle moves with knob movement and verify accuracy throughout the adjustment range.
Reticle calibration - confirms the reticle is properly dimensioned by comparing it to the test target.
Reticle cant test - moving the elevation knob should move the crosshairs up and down on the vertical line. Any divergence indicates that the reticle is not parallel to the erector.

Here'a a view through the scope.

http://i27.photobucket.com/albums/c173/tkulin/CIMG5353_zpsd0fc5272.jpg

A view of the test set up.

http://i27.photobucket.com/albums/c173/tkulin/CIMG5351_zpsb1996b2b.jpg

Finally, I put the USO up and ran it through the test. Interestingly, USO had mounted it in my Bobro mount after some warranty work. I specifically asked them to mount it with the reticle vertical to the mount, but I found it to be off by about a degree. Not huge, but enough to warrant loosening the rings and fixing it.

http://i27.photobucket.com/albums/c173/tkulin/CIMG5358_zps277b37ae.jpg

I've tested a half dozen scopes with this setup, and it appears to work well. Problems with scopes are extremely obvious. In the past I've found the following:

Reticle canted 5° - Leupold
Scope would not return to zero, 1/2 MOA of slop - Leupold
Click value advertised as MOA, was really IPHY - I forget which scope
Internal level out of whack - USO
Scope not mounted level in rings - every one I check

Scopes I've tested that have been perfect: 2 Nightforce NXS's, USO SN4 (once parallax was fixed and the internal level calibrated by the factory), Millett TRS-1.

Note, none of these tests address the quality of the glass, only mechanical function. I'll probably add some resolution testing or whatever is appropriate next time I run some testing.

[BigBear]

Interesting stuff. Thank you.

Off Topic: Do you actually fire from that position? I see the road and Stop sign out there, lol. (sarcasm my friend, [ROFL2])

[asmo]

Awesome! I have always wanted to do this but dont have the tools to machine a perfect setup. Would you be interested in trading beers for time on your rig? I would love to prove that a couple of my scopes are totally plumb and good.

[Tim K]

I forgot to add a formula I derived to estimate the error due to a canted rifle.

E=error, the horizontal shift from point of aim to point of impact
A=the angle the rifle is canted
H=the height of the bullet's trajectory or the bullet drop

E = H X tan A

For example, at 425 yards, my .260 drops 28". Assume I cant the rifle 5° (easy to do due to reticle misalignment or just getting fooled by terrain)

E = 28" X tan 5°

E = 2.5"

Down at a PD match, if you hold center and are off by 2.5", you miss.

[Tim K]

Awesome! I have always wanted to do this but dont have the tools to machine a perfect setup. Would you be interested in trading beers for time on your rig? I would love to prove that a couple of my scopes are totally plumb and good.

Anytime.

[C Ward]

Mike F built a similar jig to your's to do those tests and we found that on 2 different USO's that appeared good on the test grid still showed errors when shooting . We both came to the conclusion that in the end you've got to actually shoot a box test to be 100% certain .

[Tim K]

Recoil could be a factor. I agree it's not proven till it shoots. It sure catches obvious problems in a hurry, and it's particularly well suited to getting your scope mounted level. Much easier (and more precise) than some of the other methods I've seen and tried.

[TheBelly]

this is much more suited to the nerdiness that I am accustomed to.

I approve and will now build my own once in texas.

my wife does NOT thank you for this, btw.

[newracer]

Very cool. Taking out the error in the equipment shows how much error there is in the user.

[TheBelly]

Very cool. Taking out the error in the equipment shows how much error there is in the user.


This shooter (pointing to myself) has more errors than should be allowed by law.

[67rschev]

Nice set up ! Makes my plumb line and Level Level Level seem archaic . I think you and the Mrs's should have an old fashion pot luck one afternoon for us COAR15 folk , we bring some good food , drink , ( And our favorite glass ) and you spend all afternoon running our scopes though your set up [Coffee] REALLY !

[TheBelly]

the good part about this is that it also tests the accuracy of the hardware/workmanship/tracking of the scope itself.

[Tim K]

Nice set up ! Makes my plumb line and Level Level Level seem archaic . I think you and the Mrs's should have an old fashion pot luck one afternoon for us COAR15 folk , we bring some good food , drink , ( And our favorite glass ) and you spend all afternoon running our scopes though your set up [Coffee] REALLY !

You're welcome to come play with the toys here, or even borrow them for your own use. The concrete benches down at Pueblo Sportsams club or whatever it's called would be ideal. If you or anyone else want to check a scope, I could bring the jig and the target to a PD match and set it up on the 300y range (assuming I can get permission to do so). Or, just come up some afternoon and we'll set it up in the yard again. It only takes 10 minutes to get it all ready.

I find I enjoy the testing. It'd be even more fun if we added some tests for the quality of the glass.

[TheBelly]

I find I enjoy the testing. It'd be even more fun if we added some tests for the quality of the glass.

if you have a method for testing the glass, I'm very anxious about this. I'm 'optically challenged' so looking through an initial set of lenses (glasses) just to get to the scope itself hinders my own subjective thoughts about glass.....

[Tim K]

The test methods and tools exist, but I have spent no time looking for them. One guy suggested paint chips in various colors as a good test. One set on the target and another at the viewing station so you can see what you should be seeing, so to speak. There are also standard resolution test targets, but I've never seen one in person.

Glass quality has always been a distant second in terms of importance to me, but it would be fun to try to evaluate it.

[Scogin]

Hey Tim, I know I have yet to get my scope lined up perfectly level and would definitely like to meet up and get some help fixing it. I want to start shooting PD matches and know I need to get this fixed first.

As for testing glass, could you use the same test photographers use to test distortion in camera lenses?

24191

[Tim K]

Hey Tim, I know I have yet to get my scope lined up perfectly level and would definitely like to meet up and get some help fixing it. I want to start shooting PD matches and know I need to get this fixed first.

As for testing glass, could you use the same test photographers use to test distortion in camera lenses?

24191

I'll bet that might work. Come on down and we will get you dialed in.

[67rschev]

You're welcome to come play with the toys here, or even borrow them for your own use. The concrete benches down at Pueblo Sportsams club or whatever it's called would be ideal. If you or anyone else want to check a scope, I could bring the jig and the target to a PD match and set it up on the 300y range (assuming I can get permission to do so). Or, just come up some afternoon and we'll set it up in the yard again. It only takes 10 minutes to get it all ready.

I find I enjoy the testing. It'd be even more fun if we added some tests for the quality of the glass.

This sounds like an open invite , and one that I will be sure to make . It would be great if we could get quite a few of us together for this , and compare the different levels /brands / pricepoint of quite a few optics and run them through their paces . Not to mention it would be nice to put some faces to user names I see here with the same shooting interests . Having more than one objective eye through a scope would help , as I have found that what sometimes I call a great piece of glass for my vision may not work for another and vice-versa . Another twist is I personally have looked through two of the same model of scopes ( NF ) and had complete opposite opinions of the quality GO FIGURE ?

[jmg8550]

So do you use that setup to mount your scopes level in the rings? And then from there, mount it to the rifle?

[Tim K]

So do you use that setup to mount your scopes level in the rings? And then from there, mount it to the rifle?

Exactly.

[mikeh1911]

I use a similar way to check my scopes. Here is a pic of a the measuring piece I use to check my scopes for cant and actual value of elevation click adjustments for my scope.

I have drilled a hole in the top and center of this metal piece so I can hang it on a 1 inch x 2 inch x 7 foot piece of wood. This metal piece has white marks for MOA and yellow for Mils. It is marked every 5 Mils and 10 MOA. A total of 20 Mils and 60 MOA. I used a metal tape to measure exactly 100 yards from my vice in my shop to where the metal stand with my piece of metal measuring piece is. The laser rangefinder are not accurate enough so I use a metal measure tape to get the utmost accuracy.

[TheBelly]

I tried a rough version of the vertical line to test for tracking accuracy within the cope. It works pretty well using a string and a plumb bob. At 50m it doesn't show too much weirdness in my Leupy, but the reall tell is whether or not it can track accurately at farther distance. This (thread) is excellent simple ingenuity as the weather gets nicer and everyone knocks the dust off their rifles and optics for another great shooting season.

[Kraven251]

I have used a similar setup when mounting optics, but recently discovered that the scope isn't always straight on the rifle, due to issues with base mounts or inconsistencies in milling.

Nothing against your setup, I love it, but curious about designing something that would allow this with the optic mounted on the rifle

[Tim K]

I just tested a brand new NF NXS 5.5-22 X 56 for a friend. Perfect as always.

[mikeh1911]

I can use my set up with just the scope or with a rifle rest and the scope on the rifle.

[mikeh1911]

This is another way to show students about mil and moa scope adjustments. The rifles are put in a rifle rest and the target set up at 100 yards. This lets the students see what happens when they adjust their scopes.