Easy Centering of a Scope's Adjustment Dials with a Mirror - Page 3 - Graybeard Outdoors
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post #21 of 24 (permalink) Old 01-01-2017, 08:52 PM
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Originally Posted by gcrank1 View Post
The trig works for windage, and it would for elevation if there where no bullet trajectory to account for, so yes, 4"@50yd pretty much is 8"@100yd. for all practical purposes.
I dont quite get your 'off by 1.5" at Obj. Len = [email protected]' example. Do you mean your POI is off by 1.5" @ 100yd. from your POA and how many thou' does that equate to at the scope mounts/bases?
Nothing to do with the mounts, just the scope itself:

The maximum difference I had, between half the number of total clicks, and what the mirror method proved, was 6 clicks.

6 clicks times 1/4" equals 1.5". Had I not done the follow up with the mirror, and just say my drill & tap is perfect, and there is zero wind, I was wondering how far off I would be, windage wise, at distance. I never heard of the mirror method before Tim told me, and I am intrigued.

Keep in mind, I'm just curious, and asking the same as I would, if a bunch of us were sitting down, chatting about scopes, over a beer.
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post #22 of 24 (permalink) Old 01-01-2017, 09:44 PM
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Easy enough, shoot it at 100 to be on paper and give it six clicks, repeat. It will let you find out if that 1/4 moa adjustment is close to true or not (I suspect it is somewhat nominal).
I would be thrilled to be within six clicks as I have found that the objective lens on the couple I checked rocks a tad on the flat mirror and there is a bit of diff to be seen in the crosshair position when one does. What the mirror method does for me is avoid all that really unnecessary cranking to the extremes of the mechanical adjustment, something I try to avoid with 'precision' instruments, and it is WAY fast and easy. We have to final sight in anyway.

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post #23 of 24 (permalink) Old 01-02-2017, 03:46 PM
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Quote:
Originally Posted by gcrank1 View Post
The trig works for windage, and it would for elevation if there where no bullet trajectory to account for, so yes, 4"@50yd pretty much is 8"@100yd. for all practical purposes.
I dont quite get your 'off by 1.5" at Obj. Len = [email protected]' example. Do you mean your POI is off by 1.5" @ 100yd. from your POA and how many thou' does that equate to at the scope mounts/bases?
The 1/4" per click (or moa) is at a quoted 100 yards so when you moved 6 clicks you are not off 1.5" at the obj. lens but actually at 100 yards. If you knew the distance from the cross hair to the mirror then the movement at the obj. lens could be calculated and show the difference between mechanical and optical center. I'm certainly no math wiz but using the distance of 6" from the cross hair to the obj. lens I get a difference of .001745 moa.


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post #24 of 24 (permalink) Old 01-03-2017, 10:06 AM
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Thanks Bruce, that's what I was thinking, but didn't know if I was asking correctly


Quote:
Originally Posted by BruceP View Post
The 1/4" per click (or moa) is at a quoted 100 yards so when you moved 6 clicks you are not off 1.5" at the obj. lens but actually at 100 yards. If you knew the distance from the cross hair to the mirror then the movement at the obj. lens could be calculated and show the difference between mechanical and optical center. I'm certainly no math wiz but using the distance of 6" from the cross hair to the obj. lens I get a difference of .001745 moa.


Bruce
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