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Old December 28, 2021, 08:30 PM   #1
TBL004
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2 MOA RDS

Anyone know the diameter of a 2 MOA RDS dot? TIA
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Old December 28, 2021, 09:14 PM   #2
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The “sight”??? All sights are different. You will need to be specific. (Aimpoint, Trijicon, Vortex etc. etc. )

If you are taking about the dot, 2 MOA is approx 2 inches at 100 yards. This might help as far as dot size at ranges

https://cmore.com/DotSize
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Old December 28, 2021, 10:32 PM   #3
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are you talking about the actual diameter of the dot itself inside the optic? or how big it appears on the target?

actual dot size, no idea.

1 MOA is roughly equivalent to 1in at 100yds, 2in at 200 yds, 3in at 300yds. Thus a 2moa dot would be 1in at 50yds 2in at 100, 4in at 200, 6in at 300 and so on.
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Old December 28, 2021, 11:05 PM   #4
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Was interested in the diameter of the red dot on a Holosun HS403R. Believe it has a 20mm objective lens. Thanks
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Last edited by TBL004; December 29, 2021 at 10:17 AM.
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Old December 29, 2021, 01:49 AM   #5
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https://holosun.com/index/product/detail/id/132.html

"2 MOA Dot Reticle"

Double everything below:



If for some reason you're actually asking the diameter of the dot, here's a faux scientific guess.

Assuming the dot is meant to be viewed 6" from your eyeball, the dot is about 0.00349".


Last edited by zoomie; December 29, 2021 at 02:18 AM.
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Old December 29, 2021, 10:16 AM   #6
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Thanks everyone for the replies and info. Appreciate it!
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Old December 30, 2021, 03:29 PM   #7
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A quick way to determine the size of 1 MOA, in inches, at a given distance is to divide the distance in yards by 95.5

For example, at 25 yards, 1 MOA is 25 yards / 95.5, which is about 0.26". To find the value of 2 MOA at that distance, just multiply the 1 MOA value by 2. That means 2 MOA at 25 yards is about 0.26" x 2, or about 0.52"

Another quick example.

At 238 yards, the value of 1 MOA is 238 / 95.5, or about 2.5" If you wanted to know how much 5 MOA is at that distance is, you would multiply that value by 5. So 5 MOA at 238 yards is 2.5" x 5. About 12.5".
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Old December 30, 2021, 03:54 PM   #8
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I did not know this. Thanks.

....The more you know.
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Old December 30, 2021, 05:05 PM   #9
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The exact value is actually pretty easy to find, too, if your smartphone calculator has pi. Just remember that at 300 yards a moa is subtended by exactly pi inches. Thus, you just divide your range in yards by 300 and multiply the result by pi to get exact inches. For example, suppose your range finder tells you your target is at 750 yards:

750/300 = 2.5 and
2.5×pi = 7.85398 inches per moa.
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Old December 30, 2021, 08:48 PM   #10
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A lot easier just to take a minute of angle as an inch per hundred yards.
At 1000 yards, an IPHY is 10", a geometric MOA is 10.47".
Can you hold half an inch at a thousand yards? Can you see half an inch at a thousand yards? I can't.
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Old December 30, 2021, 08:50 PM   #11
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I was thinking like zoomie, the actual emitter is a teensy fraction.
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Old January 1, 2022, 01:17 AM   #12
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Hopefully someone more articulate can explain this better than me, but there is another point to consider.

My aimpoint claims the dot is 2MOA, and perhaps it is. However, the brightness level makes the dot expand or grow.

At its lowest visible settings, to my eye, the dot covers an area of the target roughly equivalent to 2 or 3 MOA.

At its brightest, it seems to cover 8-10 MOA. I think the popular nomenclature for this phenomenon is bloom, and the effect seems to vary slightly between sights, users, power levels, and ambient light.

Just one more thing to be aware of. For best accuracy, I try to sight mine in using the lowest power level I can.
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Old January 17, 2022, 03:17 PM   #13
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Competitive shooters in the USA using bullseye targets with scoring rings spaced in inches have used the "inch per hundred yards" method for over a century. Their aperture rear sight had 40 tpi leade screws and 12 clicks per turn so a 30 inch sight radius had exactly 4 clicks to move the LOS angle exactly 1 inch per hundred yards of range
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Old January 17, 2022, 10:45 PM   #14
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The dot is a nominal 2 MOA, or 0.0333...degrees. The angle starts with its apex at your retina. The sides of the angle, if you spin them around the centerline between them, trace the sides of a cone whose axis (that centerline) passes through the middle of the red dot and whose sides just kiss its outer edges. The sides keep spreading out as you go further from your eye. At 100 yards they have spread to two inches and change. At 200 yards, they have spread twice that much, and so on.

A simple way to look at it is, the dot covers a two-inch circle at 100 yards. At two hundred yards, where the same target looks half as big in the optic, it will cover a four-inch circle. The further away the target is placed, the smaller it looks, so the more inches that same dot covers.

As to the physical size of the dot, it depends on the design of the optic. If the the field of view is 20 mm wide and your eye is six inches from the focus, and the magnification is 1X, you have about a 450 MOA field of view, so the dot would appear to be a 225th of 20 mm, or about 3.5 thousandths of an inch. That's awfully small, so I assume the field of view is actually smaller, but the product description doesn't say.
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Old February 26, 2022, 05:30 PM   #15
Bart B.
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The trig value below was calculated to 102 decimal places for those wanting more precision with trigonometry.

1.04719753642832854694747069666400334739860873986429
830552235157457471965151538005004775737357536725837... inches per 100 yards...

Use one inch.

Last edited by Bart B.; February 26, 2022 at 05:47 PM.
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Old February 26, 2022, 05:49 PM   #16
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What about if the distance is 240 yards?

Then if one is fixated on using whole number values, one might assume that the correct rounded value for 1MOA at that distance is 2" when it's actually 3".

Knowing the proper value doesn't mean you have to use all the digits--in fact, as the example shows, it can be even more important to know the proper value if you're going to round.
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