Mrad vs mil vs MIL

[WesternSlope]

Was playing around with JBM ballistics today and noticed on the drop down menu for drop and windage it has mil and mrad as options. I had thought they were the same. To make matters more confusing, one is abbreviated MIL in all caps while the other is abbreviated mil in lower case. When I selected both side by side I found they were close but not the same starting at 325 yards. Interestingly, they also have cm/100m as a drop down option which I would have thought was also the same. When googling this, the closest answer I found was on the Schmidt and Bender website which references that the NATO standard for mrad is 0.98 true mil’s but doesn’t explain why.

Can anyone explain?
Also which is my swfa 6x? MIL or mil?
Thanks,
Tom

 

[WesternSlope]

On a Wikipedia article about milliradians there is an explanation of common approximation errors. One of which is where the curved 1000th of a radius is approximated as the straight linear line alongside the curve. My hunch is that accounts for the difference. Still though, which is my SWFA scope?
Attached is a screenshot from the Wikipedia article showing the orange straight line vs the blue curved line.

 

[Fire power]

As far as I know they are the same thing. And like you noted, they are milliradian. Yes, the terms would be interchangeable.

 

[WesternSlope]

As far as I know they are the same thing. And like you noted, they are milliradian. Yes, the terms would be interchangeable.

Yeah but why the difference in numerical data? It’s slight I know but I’d still like to understand the “why”.

 

[Mike Islander]

0.1 MIL (NATO) is actually 0.098 MRAD. Scope makers use both terms (MIL and MRAD) to mean 1/1000 of the range. SWFA click is 0.1 MRAD, so 1/10000 of the range; 1 CM at 100 meters, 10 CM at 1000 meters, etc. The error is tiny at small angles:

3.3×10−7% (or 3.3 parts per billion) error for an angle of 0.1 mrad, for instance by assuming 0.1 mrad equals 1 cm at 100 m.

 

[WesternSlope]

Thank you.

 

[WesternSlope]

Mike, why is that? I thought the difference between the curved line and straight line would explain it but that doesn’t make sense. We’re still looking at the angular measurement not the linear measurement. So why the difference?

 

[WesternSlope]

Alright after some reading, I’ve learned there’s 6,283.185 mrad per circle. NATO standard is 6,400 mil per circle to make math easier. All of this is pretty theoretical since I can’t shoot the difference and even if I could, Id need to go off field data not just calculations anyway.

 

[Mike Islander]

Mike, why is that? I thought the difference between the curved line and straight line would explain it but that doesn’t make sense. We’re still looking at the angular measurement not the linear measurement. So why the difference?

Edited:

MRAD is the actual arc length. It is (of course) longer than the straight line between the two ends of the arc and longer than the NATO mil.

Scope manufacturers use both terms, MRAD and Mils, to mean 10 cm at 100 meters. 0.1 MRAD/Mil = 1 cm at 100 meters. The error at small angles is negligible.

 

[Sled]

6283 mrad vs 6400 mils. With artillery, on the pantel azimuth (left/right) there are 32 hashes with a value of 100 each. That equals 3200. Turn it around to face backwards and you have the same numeric values of 3200. Add them together and you get 6400 mils per circle. That's a nice round number that you can do math with quickly.

Elevation is a bit simpler but a mil is still a mil.

 

[Fire power]

A Radian is a way of expressing an angle. If you take any circle and measure the radius (the distance from the center to the outer edge) and overlay that distance along the circumference of the circle, the starting and ending point of that distance represents a pie-shaped figure which is an angular measurement called a Radian. A Milliradian is that same distance divided into 1000 sub-parts. Radians were "invented" as a mathematical technique in England in the late 1800s.

Alternately, some people use degrees (as with the MOA system) which is based on breaking-up a circle into 360 pie-shaped pieces. The number of 360 pieces came from long ago when it was believed there where 360 days in one year. The exact era and civilization of folks who established that is lost to history -but, the method survived the test of time

 

[BBob]

Scope makers use both terms (MIL and MRAD) to mean 1/1000 of the range.

Early March Compacts (other March's at the time may have been as well) were .098 scopes. There was some confusion when they first came out and people were reporting they weren't tracking correctly. They actually were, they just needed a correction in the ballistic solvers to chart it correctly. March changed/corrected it later to match everyone else.

 

[Macintosh]

So are there ANY currently manufactured scopes with mil=.098? My understanding was pretty much all mil scopes are 1cm@100m. I think the above is confirming this, but not certain.

 

[Mike Islander]

So are there ANY currently manufactured scopes with mil=.098? My understanding was pretty much all mil scopes are 1cm@100m. I think the above is confirming this, but not certain.

My wild guess is that only artillery might possibly use 0.098, but I am truly guessing.

 

[Mike Islander]

Cool thing about radians is that there are exactly 2*pi radians in a circle. This allows us to get exact numbers with math involving angles.

There is also orders of magnitude less error using Mils than MOA when converting to measurements. About 3.3 parts per billion for Mil scopes assuming 1 cm at 100 meters versus about 5 parts per hundred for MOA scopes assuming 1" per 100 yards. Not that it matters much at the distances we shoot rifles.

 

[DangerRanger]

Iirc the old Marches, maybe like 10 years ago? We’re nato mil

That’s the only ones I’ve heard of