MOA vs MRAD

[E.Shell]

Regarding the OP's question: I'd suggest that there is no real difference, but mils will be more popular and thus it will present an easier crossover to other shooters. Most Americans actually find it easier to quickly relate to the MOA system, because it is roughly an inch every hundred yards, but neither systems is at all complicated.

Radian is the derived SI unit for angles. Yes, radian and miliradian are metric units.

No sir, a radian and its parts are not metric.

Check the definition and the way in which a radian is derived. It is an angle with a simple ratio in which the length of the arc is equal to the radius and can be applied to any size circle. Nowhere in the wiki discussion of this angle does the word "meter" appear.

https://en.wikipedia.org/wiki/Radian

When the angle of the arc subtended by a radian is divided by 1,000, the resulting angle is a milradian, which is currently under discussion.

Again, as Pinecone, TheBulge and others state above, the resulting milradian (milrad/mrad/mil) is a simple ratio of 1 to 1,000 and it forms/defines an angle with a constant ratio, not a distance:

A milradian is:
1" at 1,000 inches
1 yard at 1,000 yards
1 meter at 1,000 meters
1 mile at 1,000 miles
1 parsec at 1,000 parsecs, add infinitum...

The thing that makes people draw the wrong conclusion is that the customary adjustment on a mil based scope is 1/10th of a mil, so our changes are in base 10, making the decimal system a commonality with the metric system. At 100 m, one click is then 1 cm. Only a convenient coincidence though, as can be seen by the following:

Consider this:

Assertion:
The metric system is based upon the absolute length of a meter, subdivided or multiplied by powers of 10.

Questions to provoke analysis:
If subdivisions of a yard were expressed in 10ths/100ths, would it then be an Imperial scope? (yes, at 100 yards, one 1/10th mil click would be 1/100th of a yard.)

If a meter was 45" long, would a mil scope still be metric? (yes, because the ratio would still be 1:1000 and one click at 100 45" meters would still be 1/100th of a 45" meter)

If a meter was subdivided into 25ths instead of 10ths, would a mil scope still be metric? (no, because the length of a meter is not the commonality, only the decimal division is)

If the mil scope adjusted in 1/4 mil increments vs 1/10th, would it still be a metric scope? (no, because we abandon the only commonality to the metric system)

How can the way a radian is derived from a dimensionless circle (and it is) indicate that it is somehow metric? (it does not, a radian is a relationship of relative lengths that define a specific angle, not a distance)



Understanding the answers to the rhetorical questions above will mean you understand that the mil is only a geometric unit of angular measure, a ratio and relationship of lengths, and not a specifically metric metric unit.

 

[RwWilly]

And then the military has to "help"!
https://en.wikipedia.org/wiki/Milliradian#Millieme
There are 2000π milliradians (≈ 6283.185 mrad) in a circle; thus a milliradian is just under 1⁄6283 of a circle, or ≈ 3.438 minutes of arc. Each of the definitions of the angular mil are similar to that value but are easier to divide into many parts.

1⁄6283 The “real” trigonometric unit of angular measurement of a circle in use by telescopic sight manufacturers using (stadiametric) rangefinding in reticles.
1⁄6400 of a circle in NATO countries.
1⁄6000 of a circle in the former Soviet Union and Finland (Finland phasing out the standard in favour of the NATO standard).
1⁄6300 of a circle in Sweden. The Swedish term for this is streck, literally "line". Sweden (and Finland) have not been part of NATO nor the Warsaw Pact. Note however that Sweden has changed its map grid systems and angular measurement to those used by NATO, so the "streck" measurement is obsolete.

 

[traveller]

Understanding the answers to the rhetorical questions above will mean you understand that the mil is only a geometric unit of angular measure, a ratio and relationship of lengths, and not a specifically metric metric unit.

The BIPM lists it as the derived unit for the measurement of angles.

http://www.bipm.org/en/publications/si-brochure/section2-2.html

Yes, it's a dimensionless number, it is still part of the SI and not an imperial or USCS unit.

 

[smdub]

No sir, a radian and its parts are not metric.

Check the definition and the way in which a radian is derived. It is an angle with a simple ratio in which the length of the arc is equal to the radius and can be applied to any size circle. Nowhere in the wiki discussion of this angle does the word "meter" appear.
...
Understanding the answers to the rhetorical questions above will mean you understand that the mil is only a geometric unit of angular measure, a ratio and relationship of lengths, and not a specifically metric metric unit.

Metric is more than meters. Grams, Kelvin/Centigrade, etc for example. Radians are the accepted SI unit for angle. They are therefore metric. How many kids are taught to throw a ball up at pi/4 vs 45deg in the states? Ever seen a radian protractor here?
As you point out the ratio, being dimensionless, will work conveniently in either unit of measure.

The BIPM lists it as the derived unit for the measurement of angles.

http://www.bipm.org/en/publications/si-brochure/section2-2.html

Yes, it's a dimensionless number, it is still part of the SI and not an imperial or USCS unit.

^ This.

 

[Pinecone]

Then for fun, there are different number of milliradins in a circle for Army and Marines.

Army = 6400 in 360 degrees
Marines = 6283 in 360 degrees

Mils are NOT metric. The have been accepted as the SI units.

If they were truly metric, the circle would be divided into some multiple of 10 units (1, 10, 100, 1000, 10000, etc) then those subdivided.

Second and Ampere are SI base units, so does that make our time metric?

And while milliradians are used, do you ever use centiradians? Or picoradians? Or kiloradians? Or any of the other metric prefixes.

 

[smdub]

And while milliradians are used, do you ever use centiradians? Or picoradians? Or kiloradians? Or any of the other metric prefixes.

They are. Describe the total angle of rotation of something like a spring or a wound fiber. When you write a cnc program to cut a fine spiral on a 4th axis it can be in the thousands of total radians. urad(micro), nrad(nano), etc are used in astronomy. Just because YOU don't use them doesn't mean they aren't common in other fields.

 

[Magnumite]

I believe the point is radians, mrads are not metric. As pinecone asserted the circle is not divided into functions of ten nor multiplied as such. The radian itself is not a function of ten (57.296 degrees). The linear behavior of the arc/radius relationship is being identified. Using the logic radians are metric is akin to saying thousands and hundreds of an inch are metric because they are multiples of ten measurement. Radians are an international unit of measure, based on the arc/radius length.

 

[Wayne1one]

Can someone break it down real simple for me?

Lol, that turned out well

Sent from my VS990 using Tapatalk

 

[Magnumite]

Post #21 above by E. Shell, center of post breaks it down as well as it can be done. If one is looking for a formula, then choose the 1/1000 value in any unit system, divide it by 10 and the result will be the 100 yard/meter equivilent. The shooter still needs to do a little math.

 

[Pinecone]

Actually math only needed if you are trying to range with the reticle.

Otherwise, you (or your spotter) spots your shot 2 smoots low, you dial up 2 smoots and shoot again. The smoots could be mils, minutes, furlongs, etc.

 

[Indiana Jones]

Actually math only needed if you are trying to range with the reticle.

Otherwise, you (or your spotter) spots your shot 2 smoots low, you dial up 2 smoots and shoot again. The smoots could be mils, minutes, furlongs, etc.

Well put. I was hesitant to learn mills but when you are actually shooting after you have confirmed dope, they are the same damn thing. Just numbers on a turret. Once I got that through my skull, it clicked. I can switch between MOA and and Mil scopes all day now.

 

[Magnumite]

At the range, I range along with just using the scale on the reticle to adjust. That way I could understand my load and shooting more.
I am sure the ballisics and parabolic path comment will come up but more an understanding approach than a rote memorization.

 

[smdub]

As pinecone asserted the circle is not divided into functions of ten nor multiplied as such. The radian itself is not a function of ten.

Its a function of one, not ten. The point of a radian is that one meter radius * 1 radian = 1 meter arc length. Nothing else could be dimensionless. 1m*1=1m. This allows lim(x->0) sin(x) = x. Which then allows for the clean taylor series expansion of sin(x). No other scaling would allow these to be mathematically 'clean'. Using a scaling of 1 is a full circle would bury 2pi, and the roundoff error it must bring along, into lots of things where it doesn't belong. W/ radian being defined the way it is you can calculate linear distances of a triangle, which is done way more often than full circles, without EVER involving pi.

FWIW, a function of 10 has nothing to do w/ metric. A circle being something like 10 radians is even dumber. One is the standard. 1 m, 1 kelvin, 1 kg, etc. (assuming mks.) Everything else is just scientific notation to make larger/smaller. A billion dollars isn't metric. Its just math. Some of the fundamental units of the metric system have goofy constants associated with them (amp and lm notably, heck, even the meter definition uses a 2.998e8 constant now.) Doesn't make them non-metric.

 

[Magnumite]

So what is the point? I understand the metric system as do many others here. I unsterstand angle and arc. The point of the ten base was brought up as evidence the mrad is metric, which has been debated it is not.

I support one member in his point then he comes back on me stating math isn't needed in a math based discission. Now this...yes, I can keep up, been awhile since I took those calculus courses in an engineering program.

Not posting is more productive.

 

[smdub]

So what is the point?

TL/DR:
SI *is* the metric system.
The radian is the unit of angular measure in the SI.
t.f. radian is metric.

The point of the ten base was brought up as evidence the mrad is metric, which has been debated it is not.

No. The point was made that other than mrad, radians were NOT used w/ prefixes and therefore NOT metric. Negative logic that was demonstrated false (and a moot point anyway.)

 

[Indiana Jones]

Mountain/molehill. Shooting long range is NOT hard. Much like reloading, people turn it into special black magic voodoo. It takes basic knowledge and practice and a good amount of ammo. Go out, and shoot...you'll learn.

 

[BigSteve57]

It seems like it's becoming a matter of common usage.
When I was taught engineering (late 70's, early 80's) the metric system was the system of measurement like meters, centimeters, millimeters, grams, kilograms etc...
It was clearly under the SI units umbrella and as young engineers we did not think of SI=metric.

But it looks like that is changing, if only in common reference, written usage or dare I say semantics.

I show the following as evidence of that shift in thinking, not that I necessarily agree with it or really think it matters much one way or another.

REF:
Is the SI the same as the metric system?
"The SI (or Système International d'Unités ) is the modern form of the metric system."
http://antoine.frostburg.edu/chem/senese/101/measurement/faq/SI-and-metric.shtml

The new SI: Proposal for a revamped system of measurement units
"Taking the first steps of what would be a major historical advance in the science of measurement, the National Institute of Standards and Technology (NIST) is participating in a worldwide effort to recommend major revisions to the International System of Units (SI), the modern metric system that is the basis of global measurements in commerce, science and other aspects of everyday life. "
https://www.sciencedaily.com/releases/2010/10/101027124746.htm

 

[traveller]

Time for the WestJet video:

 

[Pinecone]

Well put. I was hesitant to learn mills but when you are actually shooting after you have confirmed dope, they are the same damn thing. Just numbers on a turret. Once I got that through my skull, it clicked. I can switch between MOA and and Mil scopes all day now.

The only issue is if the reticle and turrets aren't the same. Or the shooter and the spotter are using different ones.

Not impossible, just some mental math required.

 

[Pinecone]

Its a function of one, not ten. The point of a radian is that one meter radius * 1 radian = 1 meter arc length. Nothing else could be dimensionless. 1m*1=1m. This allows lim(x->0) sin(x) = x. Which then allows for the clean taylor series expansion of sin(x). No other scaling would allow these to be mathematically 'clean'. Using a scaling of 1 is a full circle would bury 2pi, and the roundoff error it must bring along, into lots of things where it doesn't belong. W/ radian being defined the way it is you can calculate linear distances of a triangle, which is done way more often than full circles, without EVER involving pi.

FWIW, a function of 10 has nothing to do w/ metric. A circle being something like 10 radians is even dumber. One is the standard. 1 m, 1 kelvin, 1 kg, etc. (assuming mks.) Everything else is just scientific notation to make larger/smaller. A billion dollars isn't metric. Its just math. Some of the fundamental units of the metric system have goofy constants associated with them (amp and lm notably, heck, even the meter definition uses a 2.998e8 constant now.) Doesn't make them non-metric.

Except that 1 foot radius * 1 radian = 1 foot arc length.

So radians are English units.

Radians are NOT metric.

Even though they are used in the SI system.