Thread: Determining mil value at different magnification??

Hey guys,

One of my scopes has a mildot reticle, which ive never really used before. Ive dialed it successfully to 750 yards but in preparation for the Toby shoot im looking to use the reticle as well as dialing, as dont think ill have enough on the dial to get to 1000?

I know that 1 mil is approx 3.44 MOA, however the scope has accurate mil value at 14x, and i want to be able to use max mag of 20x

Is there anyway to calculate what the mil value will be when scope on 20x? Or i guess its just best (and simplest) to just set to 20x, and shoot a group at 100 using the centre of reticle, then shoot another group holding 1 or 2 mil holdover on same aim point on target and measure how much its moved to calculate the MOA value that one mildot is on 20x

3.44 moa ÷ 14 × 20

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Actually scratch that, working the wrong way round!

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From my own (limited) experience, and if someone has a faster way so be it, the method I use for this is as follows. It does not require shots to be fired.

At the range I want to shoot I set up a target with increments clearly marked at set heights. As you already know that the distance between your dots is 3.44MOA at 14x, then I would suggest mark that as one of your measure options. (IE a 3.44MOA circle or square at the range you want to test. I usually set up a 1", 2" 3" and 4" circle at 100m or a series of boldly defined lines of known lengths and number them. Depending on how close you are to 14x and how close your 20x is to actual 20x then I would expect the distance between your dots to be close to 2.4MOA so if you make one of the lines 2.4MOA this could confirm that.

I then go to my shooting position, set my scope to the max magnification and use the lines to measure the distance between dots. This then tells me what the distance at that range is the distance between these. As the angle will not change, I would do this at a closer range like 100m with MOA measures (or smaller if you can see them clearly, the multiply as you go out.

If you distance between the mil dots is 1.5MOA then that (angle) wont change between 100 and 1000 metres.

Does that make sense?

Originally Posted by GWH

Hey guys,

One of my scopes has a mildot reticle, which ive never really used before. Ive dialed it successfully to 750 yards but in preparation for the Toby shoot im looking to use the reticle as well as dialing, as dont think ill have enough on the dial to get to 1000?

I know that 1 mil is approx 3.44 MOA, however the scope has accurate mil value at 14x, and i want to be able to use max mag of 20x

Is there anyway to calculate what the mil value will be when scope on 20x? Or i guess its just best (and simplest) to just set to 20x, and shoot a group at 100 using the centre of reticle, then shoot another group holding 1 or 2 mil holdover on same aim point on target and measure how much its moved to calculate the MOA value that one mildot is on 20x

Your method would work as well and would be more fun that my method, but my method can be used in residential areas etc where shooting is not possible or practical.

Reverse my formula

3.44 moa ÷ 20 × 14 = 2.408 moa

Provided of course that your magnifications are correct.

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Makes perfect sense, thanks

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Buy ffp

Just shoot at 14 power if you want to use your mil dots.

I've shot 6 inch targets at 1000 and shot at the 1400 target with the 12x power on my 6.5 at brads.

Originally Posted by Wildman

Buy ffp

Yeah I do realise this now, normally I would never normally need to use the reticle like this, but I'm keen to shoot beyond 1000 at the Toby shoot and don't have a 20moa rail and probably not enough on the turret alone.

Down load strelock app on your phone and you ll be sorted.

Just found this in a comment on a review of my scope on the vortex site.

"If you have a variable power scope and the calibration (cal.) for the subtensions of the reticle is say 14x on a 6.5-20 power scope you can determine the hash mark spacing at say 6.5x, 8x and 20x. by using the following formula.
Divide the cal. (14x) by the desired power, say 6.5x or 20x and then multiply the cal. subtension size by this answer. You can now make a chart for hold over or even ranging.
Here we go. 14x/20x=.7, 14x/8x=1.75 and so on. Now take the answer, say .7 for the 20x. Multiply the answer against the cal. subtension size.
If the subtension, (mil-dot) spacing is 3.6" at 14x it will be 3.6 x .7= 2.5" @20x. 3.6" x 1.75= 6.3" @8X and 3.6 x 2.1=7.56" @6.5x"

So ive just calculated that on 20x 1 mil spacing will equate to 2.5" @100yds, so 2.5 divided by 1.047 = 2.387 MOA (on 20x), so the top of the bottom post (5 mil) gives me 11.93 MOA, so say 12 moa.

Where as on 14x that same point on reticle gives me just shy of 17.5moa.

So thats what i wanted to know. I'll double check by actual shooting at the range anyway, as the 20x may not be a true 20x eh.

Thanks for the help guys.

Originally Posted by GWH

Just found this in a comment on a review of my scope on the vortex site.

"If you have a variable power scope and the calibration (cal.) for the subtensions of the reticle is say 14x on a 6.5-20 power scope you can determine the hash mark spacing at say 6.5x, 8x and 20x. by using the following formula.
Divide the cal. (14x) by the desired power, say 6.5x or 20x and then multiply the cal. subtension size by this answer. You can now make a chart for hold over or even ranging.
Here we go. 14x/20x=.7, 14x/8x=1.75 and so on. Now take the answer, say .7 for the 20x. Multiply the answer against the cal. subtension size.
If the subtension, (mil-dot) spacing is 3.6" at 14x it will be 3.6 x .7= 2.5" @20x. 3.6" x 1.75= 6.3" @8X and 3.6 x 2.1=7.56" @6.5x"

So ive just calculated that on 20x 1 mil spacing will equate to 2.5" @100yds, so 2.5 divided by 1.047 = 2.387 MOA (on 20x), so the top of the bottom post (5 mil) gives me 11.93 MOA, so say 12 moa.

Where as on 14x that same point on reticle gives me just shy of 17.5moa.

So thats what i wanted to know. I'll double check by actual shooting at the range anyway, as the 20x may not be a true 20x eh.

Thanks for the help guys.

Thats why I use the measure method I described. If you calculate (as above) that at 20x your scope should have 2.5 MOA between Mil dots, then you can measure that by setting a 2.5 MOA target (or bold vertical line) at 100m and at 20x this line should be the same as the distance between the mil dots on your scope. (I got 2.4 MOA from my calculation)

Bear in mind that this will also be affected by how close to 14x you scope really is as well. I usually start at the maximum zoom anyway as if you are slightly off on the 14x (say 14.3x or 13.7x) then this will affect your results as well.

If you are exactly 3.44 MOA at 14x I get 2.408 MOA

If your magnification was actually 14.5 then at 20x it would be 2.494 MOA

And if your magnification was 13.5 then at 20x it would be 2.32 MOA.

The extreme spread of the variation is .174 MOA so at 100m not likely to make much difference. Thats nearly two WHOLE inches at 1000 yds..(1.74 inches to be precise,)..so if that screws your day up then you will be a far far better shooter than most of us ever could hope to be....

Yep working out the hold point at different powers is pretty straight forward. I am guessing you have a scope with MOA click adjustments but a MIL based reticle

Originally Posted by Gillie

I wrote an article on this for NZ Guns & Hunting a few issues ago. Here is an extract from that article. I was demonstrating the use of a cheap MILDOT scope on a 22LR being used to shoot out to 200m without needing to dial the scope. The exact same principle applies for what you want and the formula still works if you want to use 16x and your MILDOTs. You will need to rearrange the equation below to make it work out what you want it to.

The formula to work out how much to reduce the scope power is a straight forward ratio:

SPR = (SPA × A) / HOR

Where
SPR = Scope Power Required
A = Aiming Point Hold Over
SPA = Scope Power where the hold over is correct
HOR = Hold Over Required

For my example I want to use the 4th mildot under the centre of the cross hairs – this mildot is 4MIL at 9x power. This means for my example “A” is 4MIL and “SPA” is 9x power.
My ballistic program estimates I will need 5.4MIL of elevation to hit a target at 150m. Using the above formula this means to use the 4th mildot I need to reduce the scope power to 6.7x power (9x4/5.4 = 6.7).

DISCLAIMER!!!
You need to test this theory on your rifle and your scope. I have no idea if your scope

• has a correctly dimensioned reticle at the nominated magnification
• that your scope actually magnifies the image the amount is says i.e. it is 16x when it says it is, and all the other power line up as well
• that your scope does shift its point of impact when you change the scope power.

Mils at x yds, or moa at x metres just sounds wrong, like a holden motor in a ford. My small brain has managed to over complicate such conversions in the past resulting in embarrassment at distance. A demonstration of this may well be available at Tobys shoot.