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Rifle Scopes So, how does your scope ACTUALY adjust?

gugubica

gugubica

Gunny Sergeant
Full Member
Minuteman
Dec 13, 2005
1,714
0
Lake of the Ozarks, Missouri
I was running some tracking tests the other day on my optics.

I placed a target at 100 yards with a dot towards the botom. I measured up 36" and placed another dot. I mounted it perfectly plumb. I put 5 rounds in the lower dot with my elevation turret zeroed. I then dailed the scopes up 10 mils. Using the same point of aim, I sent five more rounds.

In theory, these should have impacted the top dot.

They of coarse, did not. That is not what surprized me. What did was the difference in scopes. Each is a good quality scope, each tracks perfectly (returns to previous positions without deviation). But, in the above test, one was .3 mils low, one was .4 mils high, one was .7 mils low (not saying the brands but lets just say that I did not expect the last one to do well).

This is not a problem as I just adjust my come up data and pro-rate it one the way down. This is actually why I do this test and why you should too.

But, it got me thinking...those of you who have done this (and again, everyone should), what are your errors/deviations? Has anyone run this test and accieved perfect results?
 
Re: So, how does your scope ACTUALY adjust?

I'm going to give it a try next time I'm out.
 
Re: So, how does your scope ACTUALY adjust?

Mine adjusts real easy. All I do is put the knob between my fingers and move it however many clicks it needs to go to the next range. I usually use the numbers as a 12 + 3(clicks after 12) and rock and roll. The adjustment on my USO's is nice and smooth with very tight clicks.
grin.gif


I do need to ask:
Why are you measuring 36" at 100M? You should only need 6MOA or 6" at 100M to test on a 1" circle or a 1/2" circle.
 
Re: So, how does your scope ACTUALY adjust?

The only test I have done is to freely placing the targets and read the distance in the reticle then adjust accordingly, and the scope tracked true. Haven't tried to measure the distance from first target to 2nd target on paper first then dial accordingly.

Interested to give it a try.

Thanks,

Dyl..
 
Re: So, how does your scope ACTUALY adjust?

I do the stepping test. Put an orange dot at the bottom and fire three bullets with my load that shoot 0.25MOA. I would get one ragged hole.

Then I dial 20 clicks (I have 0.5mils adjustment on my Zeiss) up and shoot the orange dot again. Another 20 clicks and shoot. Yet another and shoot.

What I find is the spacing between the holes are the same but for my setup, the bullet holes are very gradually drifting off to the right.

Maybe I'm canting my rifle or my scope isn't lined up properly with the bore.
 
Re: So, how does your scope ACTUALY adjust?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: CanPopper</div><div class="ubbcode-body">I do the stepping test. Put an orange dot at the bottom and fire three bullets with my load that shoot 0.25MOA. I would get one ragged hole.

Then I dial 20 clicks (I have 0.5mils adjustment on my Zeiss) up and shoot the orange dot again. Another 20 clicks and shoot. Yet another and shoot.

What I find is the spacing between the holes are the same but for my setup, the bullet holes are very gradually drifting off to the right.

Maybe I'm canting my rifle or my scope isn't lined up properly with the bore. </div></div>

i would check the scope if crosshairs are level, just did the same test on an h-s prec. rifle with a leupold 3.5-10x40 mil dot (with 1/4") same drift off the the right(about 1 week ago).

next I marked a plumb line, repeated - adjusted scope crosshairs so it impacted on the line, re checked and it seems to be tracking good now. used about 18 rds
 
Re: So, how does your scope ACTUALY adjust?

First mistake is that if your testing a mil scope you need to be at 100m, not 100y.
 
Re: So, how does your scope ACTUALY adjust?

I test all my scopes and the S&Bs(4), NF(3) and Premiers(2) have all been dead on in adjustments and reticles subtending.

I place a mark every 3.6" up to 36" and fire 2 rounds at each 1 mil adjustment keeping the same aiming point at the bottom.
 
Re: So, how does your scope ACTUALY adjust?

Thanks but haven't gotten it yet to test but will
wink.gif
 
Re: So, how does your scope ACTUALY adjust?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sniperdude</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: CanPopper</div><div class="ubbcode-body">I do the stepping test. Put an orange dot at the bottom and fire three bullets with my load that shoot 0.25MOA. I would get one ragged hole.

Then I dial 20 clicks (I have 0.5mils adjustment on my Zeiss) up and shoot the orange dot again. Another 20 clicks and shoot. Yet another and shoot.

What I find is the spacing between the holes are the same but for my setup, the bullet holes are very gradually drifting off to the right.

Maybe I'm canting my rifle or my scope isn't lined up properly with the bore. </div></div>

at least for my test that I have done with this scope/rifle, I did this more for, to check that the crosshairs are in line with the bore. (the mil-dot reticle was an aftermarket from leupold)

i would check the scope if crosshairs are level, just did the same test on an h-s prec. rifle with a leupold 3.5-10x40 mil dot (with 1/4") same drift off the the right(about 1 week ago).

next I marked a plumb line, repeated - adjusted scope crosshairs so it impacted on the line, re checked and it seems to be tracking good now. used about 18 rds </div></div>


at least for my test , mine was done only to check that the crosshairs were plumb / level with the bore. the reticle was an aftermarket from leupold
 
Re: So, how does your scope ACTUALY adjust?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Switchblade</div><div class="ubbcode-body">I do need to ask:
Why are you measuring 36" at 100M? You should only need 6MOA or 6" at 100M to test on a 1" circle or a 1/2" circle.

</div></div>

I use 36" because 10 mils equals 36" at 100 yards. I use 10 mils because it is easier.

When I measure the distance from the dot to my group and it equals 1.12 inches, I multiply that by .36 and that gives me my mil value (0.4 mils).

If my offset is 0.4 mils from the dot, that gets me my constant to use for data correction. i.e. 0.4 mils per 10 mils (what I dialed) or 0.04 mils per mil (0.4 divided by 10).

So, when my drop data is 10 mils, I would take that and multiply it by 0.04, which results in 0.4 mils I need to add to the 10 mils to account for the erector error, so my card will be adjusted to 10.4 mils. When my drop data is 3.8 mils, I multiply that by 0.04 to get a correction of 0.152, I add that to 3.8 and get a corrected figure of 3.952 (or 4.0 on my drop card).

By doing this, it corrects your drop data to account for the error in the errector system of your scope. Most scopes will not dail exacly .1 mil per click (they are mechanical after all, and there is some tolerance that must be accounted for). In the above example, this scope actually adjusts 0.096 mils per click, real close to the stated .1 mil per click, but not quite.

If the shot group would have been above the dot, you would follow the process, but subtract it from you data instead of adding it.

This might sound trivial (and it is a little), but, if your come up is 10 mils for a 1000 yard shot, the correction of .4 mils equates to a diference of over 14 inches at that distance. If you are shooting at a 1 MOA sized target, that is a miss.
 
Re: So, how does your scope ACTUALY adjust?

There is a sticky on this very forum, which details a very easy test to see that your scope is tracking properly. Do that and your gold.

You will find however that many scopes do not track at exactly 1 mil or 1 moa as they state. Your mil scope may be closer to inches per hundred yards or moa readings. As long as you are able to adjust and know the math for LR shooting, you should be fine.

Good Luck,
-Nate
 
Re: So, how does your scope ACTUALY adjust?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Rob01</div><div class="ubbcode-body">all been dead on in adjustments and reticles subtending.
</div></div>

Thanks Rob, that is what I was currious of. I own and have had scopes that are dead on. I have also had scopes that are off (some pretty high end ones even).

Again, not a huge deal as long as they dial the same every single time. But I find it interesting. I am really just currious what others experiences have been with their stuff.

And again, everyone should be doing this with every scope they own.
 
Re: So, how does your scope ACTUALY adjust?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JRose</div><div class="ubbcode-body">First mistake is that if your testing a mil scope you need to be at 100m, not 100y. </div></div>

Didn't you mean to have a
grin.gif
or
grin.gif
grin.gif
at the end of your comment...?
 
Re: So, how does your scope ACTUALY adjust?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JRose</div><div class="ubbcode-body">First mistake is that if your testing a mil scope you need to be at 100m, not 100y. </div></div>

Unless you've got a yardstick
wink.gif


I'm gonna PM Lindy and tell him you're telling people mils are metric.......
 
Re: So, how does your scope ACTUALY adjust?

I do almost the same.

But since we are measuring the scope not the rifle I just use a large tape measure set at exactly 100yds, (wider is easier to see) and set the reticle at the exact top of the tape, dial 10 mil and see what it reads. This is helpful if you plan to keep the scope and use a ballistic program since then you know exactly what the true click value is.

I recently returned a "high end" scope when it failed the test 4 times in a row.
Ross
 
Re: So, how does your scope ACTUALY adjust?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: GrimmRoper</div><div class="ubbcode-body">There is a sticky on this very forum, which details a very easy test to see that your scope is tracking properly. Do that and your gold.

You will find however that many scopes do not track at exactly 1 mil or 1 moa as they state. Your mil scope may be closer to inches per hundred yards or moa readings. As long as you are able to adjust and know the math for LR shooting, you should be fine.



Good Luck,
-Nate</div></div>

where is this sticky?
 
Re: So, how does your scope ACTUALY adjust?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MTETM</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JRose</div><div class="ubbcode-body">First mistake is that if your testing a mil scope you need to be at 100m, not 100y. </div></div>

Didn't you mean to have a
grin.gif
or
grin.gif
grin.gif
at the end of your comment...? </div></div>

nope. When I check a mil scope, I set up a piece of graph paper at 100m, then make 10cm marks down the paper.
 
Re: So, how does your scope ACTUALY adjust?

I actually like franks method best though b/c it checks the reticle and adjustments. As long as your doing your part right.
grin.gif
 
Re: So, how does your scope ACTUALY adjust?

It doesn't matter at what distance you check it, as long as you check it.

I haven't got a meter stick, but I have a yard stick, so 36 inches at 100 yards is easier.
 
Re: So, how does your scope ACTUALY adjust?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: gugubica</div><div class="ubbcode-body">When I measure the distance from the dot to my group and it equals 1.12 inches, I multiply that by .36 and that gives me my mil value (0.4 mils).

If my offset is 0.4 mils from the dot, that gets me my constant to use for data correction. i.e. 0.4 mils per 10 mils (what I dialed) or 0.04 mils per mil (0.4 divided by 10).

So, when my drop data is 10 mils, I would take that and multiply it by 0.04, which results in 0.4 mils I need to add to the 10 mils to account for the erector error, so my card will be adjusted to 10.4 mils. When my drop data is 3.8 mils, I multiply that by 0.04 to get a correction of 0.152, I add that to 3.8 and get a corrected figure of 3.952 (or 4.0 on my drop card).
</div></div>

If you multiply 1.12 inches by .36 (inches per 1/10 mil), you end up with .4 inches^2 per 1/10 milliradians, which isn't a unit you can use. You need to divide 1.12 inches by 3.6 inches per mil, which would give you an error of .3 mil.

But don't bother doing that. You could simplify your entire process by just taking the ratio of the actual adjustment (in your case it would be 10.3) to the intended adjustment (10 mils) and multiplying that by whatever is on the knob to get your actual adjustment value.
 
Re: So, how does your scope ACTUALY adjust?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: gugubica</div><div class="ubbcode-body">But, in the above test, one was .3 mils low, one was .4 mils high, one was .7 mils low (not saying the brands but lets just say that I did not expect the last one to do well).</div></div>
I won't press you too hard for the brands, but in case you're wondering that is pretty bad. The high end scopes I've measured have all fallen within +/-1% error. In fact, when they're that close they rival the accuracy of your measurement methods, so I figure that's about as good as one can expect. But with the amount of money the top end scopes cost, I do expect that accuracy from them. I paid for it dammit! With mid-level scopes I figure +/- 2% is about all you can expect. There's a reason they're cheaper. For cheap stuff, it's anybody's guess.

In other words, I hope you didn't pay too much for those scopes. If you did, I'd be sending some back.

Regardless, thanks for posting and bringing awareness to the issue. As a technical-type person, it sometimes confounds me why so many shooters do anything to avoid doing anything so technical such as measuring. A couple years ago I posted here how I measured my Falcon and found it was around 2% off IIRC. It's like I was from Mars or speaking a different language or something.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Switchblade</div><div class="ubbcode-body">I do need to ask:
Why are you measuring 36" at 100M? You should only need 6MOA or 6" at 100M to test on a 1" circle or a 1/2" circle.</div></div>
Because your rifle isn't accurate enough to discern a small percentage error in the click value by measuring over such a small distance. If your clicks were 2% off, that would put them less than 1/8" off over 6" so your rifle would need to be insanely accurate to even notice such a deviation, much less measure it accurately. Over 36", the same error will be 3/4" which is pretty easily seen with a good rifle.

10 Mils is a good standard as most scopes have that much adjustment and the math is easy. If it takes 105 clicks to go 10 mils, you're 5% off. If it takes 98 clicks, you're 2% off. You can then enter that value in programs such as JBM and adjust your drop charts accordingly. You'll find this gives much better results than what most people do--screw with the BC of the bullet in the program until it matches the incorrect adjustment of their scope such that two wrongs is making a right. Change distances or conditions significantly and the two wrongs don't make a right anymore, leading people to blame the ballistics program can't be trusted when the problem really is with their equipment.

For scopes with enough adjustment, going 15 or 20 mils is great and makes it easier to see any error. At the very least one can measure 10 mils at different spots in the range of adjustment to make sure it's consistent.

My preference is to remove the rifle's accuracy from the equation all together by using a collimator to do the measurements. Not only can you measure click value and reticle subtension that way, but also find things like dead clicks at the end of the adjustment range, reticles canted with respect to the erector's adjustments, reticles that stick and jump instead of moving smoothly, etc. You can know more about a new scope before you ever fire a shot than most people will ever know about their scopes as long as they own them as far as the precision of their adjustments go.
 
Re: So, how does your scope ACTUALY adjust?

Jon, thanks for the comparisons. These were not what I would call uber high-end optics, but one of them is in the upper-middle tier.
 
Re: So, how does your scope ACTUALY adjust?

Good info guys...

When I test my scopes, I actually prefer to do it at exactly 50yds. Doing so at a closer range affords me to more accurately discern whether the scope is tracking true, or not. First, the closer range keeps shooter error from affecting group size. And secondly, I can test more travel on a smaller piece of paper by doubling the 100yd adjustment...

Here's an old 'Hide LINK from when I gave a then new, Gen I WOTAC a 'shakedown' cruise and pics of my results...

I have since 'tested' my higher end scopes with Lowlight's method and have been satisfied with the results...
 
Re: So, how does your scope ACTUALY adjust?

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Doing so at a closer range affords me to more accurately discern whether the scope is tracking true, or not.</div></div>

Actually, not.

Any error you might make in measuring the actual range as well as the deviation from the nominal value is doubled at 50 yards what it would be at 100.

And you don't have to do that by shooting at all.

Optically Checking Rifle Scopes

If you do it by shooting, you're always running the risk of introducing both shooter error as well as the variation in POI which results from variation in muzzle velocity.
 
Re: So, how does your scope ACTUALY adjust?

I understand, Lindy.

My statement was based merely on the assumption that the average shooter can hold a tighter group at 50yds than at 100yds. The posters above referenced shooting at 100yds to test their scopes, hence my post to offer an alternative.

Your prescribed method in the provided link negates those influences entirely. Thus, a better 'mousetrap' altogether...
 
Re: So, how does your scope ACTUALY adjust?

Guys, I want to make sure that everyone knows I don't use shot groups because I think it is better. You do not have to fire a round to do this, Lindy's method is just as effective (if not more so). I simply use actual shots because I don't have the ability to have a helper dail the knob as I hold the rifle steady. This is very important, because as you are dailing the scope, you loose any point of reference (other than vertical). I also like to keep the target for future record.

In other words, don't discount any of the above methods. You really don't have to shoot to do this (or even be on a range, you can do it in your back yard). The important part is that you verify every scope you own or use.
 
Re: So, how does your scope ACTUALY adjust?

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">It doesn't matter at what distance you check it, as long as you check it. I haven't got a meter stick, but I have a yard stick, so 36 inches at 100 yards is easier.</div></div>
Since I have a gagh stick, 3000 attoparsecs is the usual checking distance.
 
Re: So, how does your scope ACTUALY adjust?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JRose</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MTETM</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JRose</div><div class="ubbcode-body">First mistake is that if your testing a mil scope you need to be at 100m, not 100y. </div></div>

Didn't you mean to have a
grin.gif
or
grin.gif
grin.gif
at the end of your comment...? </div></div>

nope. When I check a mil scope, I set up a piece of graph paper at 100m, then make 10cm marks down the paper. </div></div>

I prefer to use meters as well, my point was it isn't a requirement..

My method...with 1 cm grid

IMG_6410.jpg
 
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