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do turrets really move in MOA?

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DWilly View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DWilly Quote  Post ReplyReply Direct Link To This Post Topic: do turrets really move in MOA?
    Posted: July/04/2020 at 12:23
i understand mils and moa are a function of arc, as in angle. the the turrets are supposedly moving in an arc. i'm wondering how they accomplish this? it seems to me the turrets are moving straight up and down, the same for windage. the erector is on a ball hinge on one end and the other is being moved by the turrets, which again are moving in a straight line. the turrets are moved by threads which are a constant so are they just at a happy medium to accomplish a change which is what the angle should be? i realize we're talking about some really small numbers here but i'm fairly sure they move in a straight line, not an arc.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Travis299 Quote  Post ReplyReply Direct Link To This Post Posted: July/05/2020 at 16:10
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DWilly Quote  Post ReplyReply Direct Link To This Post Posted: July/05/2020 at 19:21
i'm sorry but it doesn't answer my question. i know exactly how a scope works which is how i can ask the question. i'll try again. the turrets move in a verticle function. moa or mils are both a function of an arc. which means each moa after the first is larger than the previous. i realize we're talking about very small numbers of difference here, but still the question remains. i don't believe turrets move in true moa but rather a straight verticle function. can anyone dispute this or explain it in detail?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote morgaj1 Quote  Post ReplyReply Direct Link To This Post Posted: July/05/2020 at 20:12
Thats a great question, I've never thought of that.  Subscribing to hear the answer.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Travis299 Quote  Post ReplyReply Direct Link To This Post Posted: July/05/2020 at 22:14

One MOA = 1.0471975511” at 100 yards which is calculated by taking the diameter of a 100 yard circle, 7200”, multiply by  PI, 3.14159 and then dividing that number by the number of minutes in a circle, 21,600,  The one MOA at 100 yards of 1.0471975511” is an arc measurement but is rounded to 1”  The 1” is calibrated on most scopes so that 1 turret click will move the POI in a linear manner or mode, ¼” at 100 yards.  This is accomplished by moving the reticle that is etched onto a glass lens in a controlled precise linear manner for the distance desired to correct the POI.

Also for your enjoyment:

Milliradians, (MRAD or Mil) and Minute of Angle, (MOA) Trivia

(Best with a 6 pack of BUD)

 

Formula for circumference of a circle = Diameter, (D) x Pi, (Pi = 3.14159.)

There are 7200” in (D) diameter of a 100 yard circle. (100 x 36” x 2 = 7200”)

Circumference of a circle at 100 yards = 22,619.448”, (7200” x 3.14159 Pi.)

1 MRAD & 1 MOA is an angular measurement at a specific distance or range.

6,283.185 Milliradians (MRAD) = 1 CIRCLE  (Pi 3.14159 x 2 x 1000 = 6,283.185, mathematical.)

6,400 Milliradians = 1 CIRCLE,  (NATO rounded MRAD.)

21,600 Minutes = 1 CIRCLE, (360 degrees x 60 Minutes in 1 degree = 21,600 minutes)

1 MOA = 1.0471975” at 100 yards, 22,619.448”/21,600 Minutes, (1” rounded.) 

1 MRAD = 3.6” at 100 yards, 22,619.448”/6283.185 MRAD, mathematical.  

1 MRAD = 3.534” at 100 yards, 22,619.448/6400 MRAD, NATO.

1 MRAD = 10 cm at 100 meters. (2 x PI x 1000 = 6283.185 MRADs in a circle). 100 meters = 10,000 cm x 2 = 20,000 cm in diameter of 100 meter circle.  20K x PI = 62,831.85/6,283.18 MRADs = 10 cm; for  (1 MRAD at 100 meters = 10 centimeters).

Scope settings MOA or MRAD.

It also depends on what your scope's notion of 1 milliradian is, because the NATO milliradian differs from the mathematical definition of a milliradian.

A mathematically accurate radian is that part of a circle where 2 * PI radians is a full circle, and a milliradian, (MRAD), is 1/1000th of a radian, so a full circle is equal to approximately 6283.185 milliradians (2000 * PI).

But the NATO definition of a milliradian for use in ballistics is that a full circle is split into 6400 NATO milliradians.

Anyway, the difference is not very large, with mathematically accurate MRADs, 1 MRAD is 100 cm @ 1000 m, with 1 NATO MRAD, it is 98.2 cm @ 1000 m. For this reason, if your scope uses mathematically accurate MRADs, 1 MRAD is about 3.44 MOAs, but if it uses NATO MRADs, then 1 MRAD is 3.375 MOAs.


 

The distance of the reticle's movement per click is tan(angle) * distance, however, at longer distances this is not exactly equal to the change in point of impact, because of the difference between changes to the line of sight and changes in the bullet's trajectory.

degrees = MOAs / 60
MOAs = degrees * 60

degrees = MRADs / (PI * 1000) * 180
degrees = (MRADs / 6400) * 360 [with NATO MRADs]
MRADs = (degrees / 180) * PI * 1000
MRADs = (degrees / 360) * 6400 [with NATO MRADs]

MOAs = MRADs / (PI * 1000) * 10800
MOAs = (MRADs / 6400) * 21600 [with NATO MRADs]
MRADs = (MOAs / 10800) * PI * 1000
MRADs = (MOAs / 21600) * 6400 [with NATO MRADs]


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tahqua View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tahqua Quote  Post ReplyReply Direct Link To This Post Posted: July/06/2020 at 07:26
Yes the reticle moves up and down in a vertical plane as it also moves left to right and vice versa in a horizontal plane. 
Doug
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DWilly Quote  Post ReplyReply Direct Link To This Post Posted: July/06/2020 at 14:40
that certainly is a lot of information, but i don't agree with you on one point. if i understand you, the turrets simply move the poi 1" at 100 yards. i know this isn't true except for a few scopes that are calibrated to do so. every tall target test i've done has the poi change very close to the 1.047 for every moa dialed. 10 moa = 10.47 inches....20 moa = 20.94 inches and so forth. this would be with quality scopes. i believe the threads are made at a pitch that works as a happy medium for the scopes amount of travel. since we are dealing with fractions of one degree for the vast majority of dialing, it's very close and works fine for practical use. and, i think the scopes move on a straight path, not an arc.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DWilly Quote  Post ReplyReply Direct Link To This Post Posted: July/06/2020 at 14:44
you also stated that it's accomplished by moving the reticle. this isn't true. the reticles are solidly mounted, it's the image that moves in relation to the reticle.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Travis299 Quote  Post ReplyReply Direct Link To This Post Posted: July/06/2020 at 16:00
10 MOA = 10.47" at 100 yards. 10 MOA = 5.235" at 50 yards.  10 MOA = 104.7" at 1K yards.

The turrets move the lens, inside the scope tube, that the has the reticle etched onto the surface of the lens which in effect moves the cross hairs to adjust the POI, with one click = 1/4 MOA at 100 yards (most scopes).  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tahqua Quote  Post ReplyReply Direct Link To This Post Posted: July/06/2020 at 16:24
FFP reticle moves and SFP erector lense moves. I was trying to say straight path as you have said.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote koshkin Quote  Post ReplyReply Direct Link To This Post Posted: July/08/2020 at 12:03
Originally posted by DWilly DWilly wrote:

i understand mils and moa are a function of arc, as in angle. the the turrets are supposedly moving in an arc. i'm wondering how they accomplish this? it seems to me the turrets are moving straight up and down, the same for windage. the erector is on a ball hinge on one end and the other is being moved by the turrets, which again are moving in a straight line. the turrets are moved by threads which are a constant so are they just at a happy medium to accomplish a change which is what the angle should be? i realize we're talking about some really small numbers here but i'm fairly sure they move in a straight line, not an arc.

The turrets are indeed moving straight up and down.  The linear movement of the turret stems, moves the reticle in the focal plane of the objective lens system (for FFP scopes, but it is conceptually similar in SFP scopes).  The objective lens system is what translates the linear movement of the reticle cell into the angular movement of the point of aim.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote DWilly Quote  Post ReplyReply Direct Link To This Post Posted: July/09/2020 at 19:39
thank you for that explaination. it makes perfect sense. i'm now wondering if the reticles themselves are etched in a linear fashion and the objective lens assembly does the same thing with them? in other words, the reticle marks are true moa or mils out to the farthest from center. and not distorted as you get away from center as i've heard some claim?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote koshkin Quote  Post ReplyReply Direct Link To This Post Posted: July/09/2020 at 20:17
Originally posted by DWilly DWilly wrote:

thank you for that explaination. it makes perfect sense. i'm now wondering if the reticles themselves are etched in a linear fashion and the objective lens assembly does the same thing with them? in other words, the reticle marks are true moa or mils out to the farthest from center. and not distorted as you get away from center as i've heard some claim?

I do not know who told you that, but it is nonsense.

The reticles are etched in a linear fashion, however the reticles are not etched in moa or mrad.  That is the wrong way to think about it.  They are etched with some dimensions that produce moa or mrad accurate angular sizing when combined with an objective length of appropriate focal length.

Combination of reticle and objective lens is what produces accurate angular gradations.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote DWilly Quote  Post ReplyReply Direct Link To This Post Posted: July/09/2020 at 21:11
agian, thank you, very informative.
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