Scope Click Values
- Thread starter Bart B.
- Start date
dmoran
Donovan Moran
Read a few scope reviews. Think you will see your question is commonly performed as part of basic turret calibration in many reviews. Next, tests like the "box test", "tall target test", or collimation are commonly used to determine and compute the actual turret error factors.
Do a internet search on scope calibration, there's lots of info, articles, and videos on the topic.
Do a internet search on scope calibration, there's lots of info, articles, and videos on the topic.
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Yes, as Donovan says, there have been many reviews that do a box test. I have a friend, Vince Bottomley who produces the Target Shooter online e-zine and although he rarely does such reviews these days tested many target scopes in all price brackets in the past. He used his 6PPC HV bench gun to test them as you really need something that groups very tightly to remove most of that variable.
Going back 15 or more years, many quality scopes had as much as 10-13% error in their click values, but by say 5 years ago that was down to at least better than 5% and in many cases 2-3% was found. A 100% accurate example must still be a rarity, but at a couple of % error it's so close as to be of little import for anything other than ELR type shooting. He never did any of the really expensive high-tech tactical / sniper type scopes that seem to abound nowadays - their adjustment accuracy would be interesting given how critical this can be for such users.
Going back 15 or more years, many quality scopes had as much as 10-13% error in their click values, but by say 5 years ago that was down to at least better than 5% and in many cases 2-3% was found. A 100% accurate example must still be a rarity, but at a couple of % error it's so close as to be of little import for anything other than ELR type shooting. He never did any of the really expensive high-tech tactical / sniper type scopes that seem to abound nowadays - their adjustment accuracy would be interesting given how critical this can be for such users.
X-Caveman
Gold $$ Contributor
As I'm sure you are aware, you'd need a special yardstick or a distance a little closer than 100 yards. One 1/4 MOA click is not .250" at 100 yards. It's .2618", so you'd hope it moved 10-15/32" over 40.
A scope checker is a great tool for doing this, BTW. If you don't have a reference scope to keep aligned with the aiming point, how else would you know your set-up didn't move from all of the clicking? A reasonable way - not talking about some tank-like rigid mount.
A scope checker is a great tool for doing this, BTW. If you don't have a reference scope to keep aligned with the aiming point, how else would you know your set-up didn't move from all of the clicking? A reasonable way - not talking about some tank-like rigid mount.
Ledd Slinger
Silver $$ Contributor
A scope checker using two optics is the most accurate way to find actual turret adjustment error. No shots need to be fired.
The reference optic does not need to be frozen, it just needs to stay on the same reference start point as the optic being tested.
So first get the "Applied Ballistics" app. Then get a scope checker and run the tall target test with an accurately marked and leveled target. Keep the reference optic on start point and adjust the other optic to whatever amounts you desire. Then check the reference optic to make sure it is still aiming at the start point.
***Keep in mind that error amounts can sometimes vary from midway to 3/4 to end of adjustment. If so find an average in the calculation below or use the value that is in the range you will mostly use. But hopefully your scopes correction factor does not vary.
Now use this calculation to determine amount of adjustment error.
Next, fill out all the applicable data in the new firearm section of the Applied Ballistics app. When you get to the "Elev. Correction Factor", enter the value from your test and calculation above. The same test can be conducted with the windage turret and entered in the "Wind Correction Factor". Now your ballistics calculator will be able to assist you with better accuracy.
The reference optic does not need to be frozen, it just needs to stay on the same reference start point as the optic being tested.
So first get the "Applied Ballistics" app. Then get a scope checker and run the tall target test with an accurately marked and leveled target. Keep the reference optic on start point and adjust the other optic to whatever amounts you desire. Then check the reference optic to make sure it is still aiming at the start point.
***Keep in mind that error amounts can sometimes vary from midway to 3/4 to end of adjustment. If so find an average in the calculation below or use the value that is in the range you will mostly use. But hopefully your scopes correction factor does not vary.
Now use this calculation to determine amount of adjustment error.
Next, fill out all the applicable data in the new firearm section of the Applied Ballistics app. When you get to the "Elev. Correction Factor", enter the value from your test and calculation above. The same test can be conducted with the windage turret and entered in the "Wind Correction Factor". Now your ballistics calculator will be able to assist you with better accuracy.
Not if the scope uses the original definition that still applies to many. Most benchrest disciplines do so multiple range aggs make sense with the all their groups using the same scale, inches per hundred yards. None require any group measured in thousandths be corrected to the trigonometric version by math and an a non exact conversation factor that has at least 102 decimal places...
1.04719753642832854694747069666400334739860873986429
830552235157457471965151538005004775737357536725837... inches per 100 yards...
How much error from a given model scope's click specs does a 3% spread in their objective lens' focal length?
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All depends on the standard and scope used. The older Unertl, Fecker, Lyman, Litchert and diSimone target scopes mounts moved .0005000" per click on a 7.20000 inch spacing. Several scopes made today have quarter inch per hundred yards clicks.
Ledd Slinger
Silver $$ Contributor
No good quality scope in production today uses 'X' inch per 100 yards adjustment, aka: "IPHY". You only find that on junk scopes and you can be sure they will have a large amount of error.
Pretty much all in MOA or MILs now. Get with the program bud! Lol
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Few, if any, are exact. Neither is their stated magnification.
Their margin of error equals half the largest group shot.
There are more precise ways that eliminate shooting system variables.
Modern day optical formulas and lens tolerances .
dstoenner
Silver $$ Contributor
That's why Vince used his 6PPC BR gun that shot in the [0.] ones in calm conditions.
tom
Gold $$ Contributor
Bart,Ledd Slinger posted in post 5 can be used if you insist on using IPHY also. You just have to change the "constant" of .0147 to .0100. The only thing it will change is the correction factor, no big deal really.
Some of today's best actually maintain their correction factors throughout their whole travel range, and some don't. It depends upon the game you're wanting to play, most are repeatable in the center few revolutions. Just like p.o.a. testing has shown, sometimes you get what you pay for, sometimes you don't.
Tom
I agree. But how do they compensate for target image in first focal plane getting bigger as range decreases and it moves further back in the scope? The erector tube lenses have to focus further back (with side focus mechanics) so it moves a smaller amount per click relative to the target image This is why click values are not constant and vary a little.
tom
Gold $$ Contributor
Bart,
I'm not sure of the answer to that one. But I have tested a 2nd focal plane reticle scope (NF ATACR) that maintains it's value all the way through it's range. Along with some 1st focal plane Kahles that maintain their correction factors. Some I've tested, like a 2.5-25 March, are quite different in the last couple revolutions. Along with noticeably poor optical performance towards the limits also.
The scope checker method is a good and easy way to test. Even with low power scopes being tested, as long as the scope taking the reading is of sufficient power, you can use a tape measure. Using an aim point I can reliably hold perfect on set at 0, I can read easily to the 64th with my 45x frozen scope.
Tom
I'm not sure of the answer to that one. But I have tested a 2nd focal plane reticle scope (NF ATACR) that maintains it's value all the way through it's range. Along with some 1st focal plane Kahles that maintain their correction factors. Some I've tested, like a 2.5-25 March, are quite different in the last couple revolutions. Along with noticeably poor optical performance towards the limits also.
The scope checker method is a good and easy way to test. Even with low power scopes being tested, as long as the scope taking the reading is of sufficient power, you can use a tape measure. Using an aim point I can reliably hold perfect on set at 0, I can read easily to the 64th with my 45x frozen scope.
Tom
tom
Gold $$ Contributor
Randy, 300 feet. Real easy to see when you're splitting a 1/16 (1/32). And I was confident to make a call to the nearest quarter point of the 1/16 (1/64) on the better days. (Remember there is a tape measure here to focus on) I felt that was about the best my human eye could do when testing p.o.a. shift also. I think sometimes when testing for shift, and a scope doesn't show a shift until the 3rd, 4th, etc.. we may just not be able to resolve much under .015".
The frozen 36x I had before the 45x couldn't resolve quite as well.
Tom
PS, I got me a 40-60 March Highmaster now. And since we don't need frozen scopes to test what this particular discussion is about, maybe I get down to the 128th
How do you all read the picture below. It's not quite to scale, the reticle in my 45 is not quite as large as this example I put together.
I'd call it about 11.015625" (ish)
Edit- After checking my notebook will all my testing data. I have numbers on POA tests wrote to the 64th, and also used the word "slight" at times. But on tall tape reading I do not see where I wrote anything smaller than to the 32nd. I did one day, but it was 50 yards (150 feet).
The frozen 36x I had before the 45x couldn't resolve quite as well.Tom
PS, I got me a 40-60 March Highmaster now. And since we don't need frozen scopes to test what this particular discussion is about, maybe I get down to the 128th
How do you all read the picture below. It's not quite to scale, the reticle in my 45 is not quite as large as this example I put together.
I'd call it about 11.015625" (ish)
Edit- After checking my notebook will all my testing data. I have numbers on POA tests wrote to the 64th, and also used the word "slight" at times. But on tall tape reading I do not see where I wrote anything smaller than to the 32nd. I did one day, but it was 50 yards (150 feet).
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