is this optic broken, or is it just me?

G

georgehwbush

New member
i have a 12x rifle scope with MoA retical and MoA target turets except they aren't. at exactly 100yds 10 inches substends exactly 10(so called minutes of angle) and adjusting the elevation (ten so called minutes of angle) moves the point of impact 11.25 inches. neither are right.

so is the scope broken or is that just me expecting things to be what they say they are, when in reality scope makers don't care what a minute of angle really is?
 
I doubt it's broken if the adjustment change is repeatable.

It's not terribly uncommon for scope clicks to be a little off the nominal value. Being off by 12.5% seems a bit high though.

That value is a bit suspicious. Are the clicks 1/8 MOA, by chance? I ask because 11.25" would be exactly what one would expect from dialing an extra 10 clicks by mistake on a scope with 1/8 MOA adjustments. Dialing 90 instead of 80 would result in 11.25" movement on target at 100yards if the adjustments are exactly 1/8 MOA.

Anyway, depending on how much you paid for the scope and how you feel about it, if the adjustments really are off by that much, you could try to return the scope. If it's a high-end product from a company that stands behind their merchandise, they will probably take it back. If they won't, it's not exactly a show-stopper. You just need to calculate how much a click actually moves the point of impact and make your adjustments based on that calculation going forward.
 
i know that most of you will already know that a minute of angle is not one inch at one hundred yards, but is .954 inch at 100 yds. but i mention that for the few that might not yet know that.

i have other scopes by the same company in mrad - mrad configuration, and they are right on. so i thought i would try one in the moa - moa setup. they will get it back, i can't work with something that is not correct and also not matching, if it was matching i could remember a conversion formula but i'm not going to try to learn how to convert their retical reading to something that will then be converted to their adjustment markings... that's too much sugar for a dime.

so is there a move by optics makers to convert the minute of angle to a "close enough" inch at 100 yds ? or what do you think went wrong with this scope?
 
i know that most of you will already know that a minute of angle is not one inch at one hundred yards, but is .954 inch at 100 yds.
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I didn't, still don't. You have it backwards.
A minute of angle is 1.04725 inch per hundred yards.
Invert and you get that 1.00 IPHY is .954 MOA.

Getting 11.25" for a nominal 10 MOA adjustment is about a 7% error. The company is not likely to say what their tolerance is. Back when American Rifleman was more technical, they would "shoot the box" with a new scope to see what its adjustments really were and would it return to zero. There were variations that you would have to put down to manufacturing tolerances and moving part slop.

But if they can make mil adjustments right on, there is no reason they can't make minute or inch adjustments right on, too. So ask them.
 
i know that most of you will already know that a minute of angle is not one inch at one hundred yards, but is .954 inch at 100 yds. but i mention that for the few that might not yet know that.
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Not exactly. Jim Watson has it right.
A minute of angle is 1.04725 inch per hundred yards.
Click to expand...
Right. It's a little over an inch. Pi/3, or about 1.047" at 100 yards.
Getting 11.25" for a nominal 10 MOA adjustment is about a 7% error. ...
Click to expand...
Pretty sure it's 12.5% error which seems a bit much to me.
no it's 1/4 moa suposedly.
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So 11.25" would be equivalent to adjusting a 1/4 MOA scope 45 clicks when the intent was to adjust it 40 clicks. I guess it could happen. but losing count and adjusting 10x extra seems more likely than adjusting 5x extra, so probably the adjustments are off a bit.

You can see if the scope maker will take the scope back if the adjustment discrepancy bothers you, or you can just calculate the actual value of a click and make your adjustments based on that from now on.
so is there a move by optics makers to convert the minute of angle to a "close enough" inch at 100 yds ? or what do you think went wrong with this scope?
Click to expand...
It's not uncommon for 1 MOA to be approximated as exactly 1" at 100 yards, nor for a scope click adjustment to be off a little. On your scope, with that much error, it almost sounds like someone used the wrong screws on the adjustments. It would be kind of interesting to see if it has the same error on the windage as the elevation adjustments or if they are different from each other.
 
(11.25 inches ÷ 1.04 Moa/inch) = 10.82 MoA
10.82 MoA ÷ 3.44 MoA/Mil = 3.14 Mil = 31 or 32 clicks (if 0.1 Mil clicks)

Doesn't seem close enough for it to be a Mil turret with MoA markings, but it may be possible.


On the other hand, the actual distance to the target should be addressed. Did you measure the distance? Or take stated distance as fact? I have seen club and public ranges have incorrect distances to the targets.
And, sometimes, people assume one unit of measurement, when a range used another. Yards vs meters, for example.

If, for example, you assumed 100 yards, but the target was actually at 100 meters (109.36 yd), 11.25" would be close to 9.8 MoA. It would look like 10 MoA, but measure 11.25" rather than 10.47".
 
My first question would be how accurate is the 11.25 inch change in POI? Are you shooting using a bench rest technique? How many shots in the group? How large is the group?

[John - check your math, I'm also coming up with about a 7.4% error which is similar to Jim's % error. 11.25" - 10.47" = 0.78" ; 0.78 / 10.47 = 0.074 (it's still 7% if you divide by 11.25 instead)]
 
One of the old tricks to (hopefully) minimize slop in the adjustment mechanism was to go a few clicks past the desired adjustment and then come "back" to it.

Worked sometimes...:rolleyes:
 
Pretty sure it's 12.5% error which seems a bit much to me.
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It is off 7% if you are working in true MOA but 12.5% if figuring in IPHY and calling it minutes.

Any road, one question is, is it a consistent error - shooting the box?
And the other is, will they replace it?

Back when I was shooting F class, I would make a yardage change assuming MOA and then tweak the scope if required. Thereafter I went by the sight setting, not nominal MOA. Are BC values better now that you can confidently work in MOA, or mils?
 
( i know that most of you will already know that a minute of angle is not one inch at one hundred yards, but is .954 inch at 100 yds. )
( I didn't, still don't. You have it backwards.
A minute of angle is 1.04725 inch per hundred yards. )

yes yes my bad. i was thinking yards to make one moa = 1 inch 95.4 but it didn't come out that way. my bad.
 
(Any road, one question is, is it a consistent error - shooting the box?
And the other is, will they replace it?)

yes it is consistent, and yes they will replace it.

(FrankenMouser) yes i measured the yardage with a 100yd tape, and the center to center of 10 shot groups with a 6ft tape which i carry in my pocket.

people i have other scopes of the same brand just in mrad-mrad not in MoA-MoA and they all seem extreemly accurate and precise. i would rather not mention the name, but it was a mil-contract, and they will get this one back.

my main question is really; are scope makers leaning toward non-MoA IPHY and calling/labeling them MoA ?

i hope that is not happening. but i fear it may be.
 
[John - check your math, I'm also coming up with about a 7.4% error which is similar to Jim's % error. 11.25" - 10.47" = 0.78" ; 0.78 / 10.47 = 0.074 (it's still 7% if you divide by 11.25 instead)]
Click to expand...
Yes, I was using the 1MOA=1inch, assuming that's how the scope maker did it.
It is off 7% if you are working in true MOA but 12.5% if figuring in IPHY and calling it minutes.
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Yes, correct.
 
my main question is really; are scope makers leaning toward non-MoA IPHY and calling/labeling them MoA ?
Click to expand...

I don't know and they probably won't tell you, or will tell you it is just a small difference.
And it is, the difference between MOA and IPHY is less than what you are seeing in click counting. The scope build is funky.

Me? I don't worry about it, the difference between a true geometric MOA and an IPHY is half an inch at 1000 yards.
 
i know that most of you will already know that a minute of angle is not one inch at one hundred yards, but is .954 inch at 100 yds.
Click to expand...

I've always understood one MOA is 1.047 inches at 100 yards.
 
I think you cannot say because one scope has error that all do. I think you will find that scopes marketed towards basic 0-200yd hunting/shooting will have more error.

Scopes marketed towards PRS, longer range hunting will have less of this issue.

There is also a brand factor here too. Some brands are better at what they do.
 
You never mention brand or model. Less expensive optics are less precise than high end optics. Some brands are less precise even with their high-end optics models.

Things like this are the difference between a $200 scope and a $1000 scope. Often the less expensive scope can be made to work if you get out and actually shoot at various ranges to see where bullets impact instead of trusting the scope to be right.
 
The adjustment tends to have more error near the extremes of the adjustment range, especially so for scope with large range of adjustments. Best is in the middle. Check a few more places to confirm.

-TL

Sent from my SM-N960U using Tapatalk
 
( I don't worry about it, the difference between a true geometric MOA and an IPHY is...)

yeah and say you are measuring a 16' gate and it reads 20.8 MoA in your retical, are you 840 or 880 yards from it? it makes a big differance at long range and used for ranging things.
 
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