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Sight Windage Graduation |
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floydthecat
Hard Corps Joined: Oct 13 2016 Location: Mississippi Status: Offline Points: 1998 |
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Posted: Jul 17 2020 at 2:34pm |
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Anyone know if there is a known relationship between adjustable rear sight windage index-marks and distance? How far does one index-mark move the POI at 100 yards? Is there such a relationship with carbine sights like it is with Garand or M14 sights?
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ncin1911
On Point Joined: Dec 13 2018 Location: Hoosier State Status: Offline Points: 435 |
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From a book I have. |
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jackp1028
Hard Corps Joined: Jan 01 2016 Location: Cloudcroft, NM Status: Offline Points: 1276 |
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The windage screw is 40 threads per inch. That's .025" per revolution. The detent ring in a carbine sight has four notches at 90 degree intervals, so each detent is .025" divided by four or .00625" per click. Assuming the carbine's sight radius is 21.5" that means one click will move the POI .956" (corrected) at 100 yards.
Edited by jackp1028 - Jul 17 2020 at 6:39pm |
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JackP
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floydthecat
Hard Corps Joined: Oct 13 2016 Location: Mississippi Status: Offline Points: 1998 |
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I think that works out darn close Jack. My reason for asking was that I was zeroing a re-barreled carbine this morning. I set a target at about 30 yards to get-on-paper and could not even get on paper. I moved the target into 20-yards and barely got on far left. I had left the windage setting where it had been prior to the barrel change. I had to crank-in several clicks right to get it on the bullseye at 20-yards. I actually wound up with the sight ramp sitting dead center of the sight rails, right where we like it. Backing up to 20-yards would turn your 3.49” per click to something like .75” (1/5th.). 5 or 6 clicks is about as far as I had to move it to get the bullseye, which equates close to your 3.49” at 100-yards. I’m old with a muddled mind, but I think my math is sorta right. |
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floydthecat
Hard Corps Joined: Oct 13 2016 Location: Mississippi Status: Offline Points: 1998 |
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I know this is correct for the Garand and the M14. Was not sure about the carbine graduations.
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PLN-TAP-7
On Point Joined: Mar 28 2020 Location: FRANCE Status: Offline Points: 117 |
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Not sure it will be of any use as it is in metric but one of my French Army manual from 1964 says: 3 graduations both sides of central line, 1 click = 1/4 of a graduation = 0.3 µ (micron) = move middle center point of 3.5 cm at 100 meter. As I went reading the part about the M1 Garand it seems that the clicks and values are the same: they give 1/4 tour = 1 click = 1/4 of a graduation = 0.3 µ (micron) = move middle center point of 7 cm at 200 meter. Hope this help.
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ncin1911
On Point Joined: Dec 13 2018 Location: Hoosier State Status: Offline Points: 435 |
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I had no idea but you got me curious and found that illustration within The M1 Carbine Owner's Guide by LarryR & ScottD on pg. 120 with some additional illustrations on pg. 121. Also found the same in some older milsurps thread replies.
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floydthecat
Hard Corps Joined: Oct 13 2016 Location: Mississippi Status: Offline Points: 1998 |
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Leave it up to me to stir up confusion I suppose.
I know at 30-yards I was not on paper, anywhere. When I moved back to 20-yards, I was left on paper. I had to move windage 6-clicks right to find the center of the bull. 1-click at 100 yards would equate to 1/5 of that at 20-yards or .2 inches per click. I moved the POI about +-1.5-inches right with those 6-clicks. So.....after going round-n-round, looks like the 1-inch at 100 yards seems correct. You know what.....I declare everybody right, because I got the carbine zero’d! 😁
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jackp1028
Hard Corps Joined: Jan 01 2016 Location: Cloudcroft, NM Status: Offline Points: 1276 |
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@ncin1911, your chart is correct for the carbine. In my calculation I failed to convert yards into feet causing an error of a factor of three. The correct number should be .956" at 100 yards. Sorry for the confusion. I will correct my original post.
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JackP
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floydthecat
Hard Corps Joined: Oct 13 2016 Location: Mississippi Status: Offline Points: 1998 |
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See....we all win.
I think I have something else to keep us entertained to post shortly. Thanks guys!
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