Why you should choose MIL, not MOA

[Hohn]

At the risk of dumbing this down...a MOA scope has 1/4 inch clicks and a mil-dot scope has 1/3 inch clicks. Is that analogy close enough?

Assuming 100y distance, that’s a reasonable approximation.

 

[Hop]

At the risk of dumbing this down...a MOA scope has 1/4 inch clicks and a mil-dot scope has 1/3 inch clicks. Is that analogy close enough?

This is the point I was trying to make. If you think in Metric then by all means go Mil.

Had you said "a mil-dot scope has 1 centimeter clicks".

Sent from my SM-G935V using Tapatalk

 

[Hohn]

0.1 Mil are 1cm clicks at 100m, not at 100y. At 100y, it's 0.36" to a 0.1 mil click. At 100m, it's 0.3937".

Just remember the 4-decimal place rule for 0.1 milc licks, and it's easy. If you are at 50y, it's 0.005 yards to a 0.1 mil click. 1800 inches= 0.18" to a click.

 

[teddy12b]

Basically using either 1/4MOA or 1/10th MIL at any distance the 1/4MOA is going to be the smaller unit of measurement if I understand it correctly.

 

[natdscott]

I replied to Nate's PM and thought I'd share a perhaps better-written post here exploring the question: how fine do my turrets need to be?

The short answer is this: your turrets need to be fine enough to matter less than your variation as a shooter with a particular rifle and ammo.


Most shooters are familiar with SD as a measure of velocity variation, but we should mostly care about Standard Deviation as it pertains to ammo grouping relative to POA. I offer the simple idea here: if the scope turret adjustment is finer than the SD of your groups, then you are a larger contributor (on average) to shot group variation than your scope zero is.

Here's a quick test to know if you need turrets finer than 0.1 MIL clicks:

1. Shoot 20 rounds of your given ammo through the given rifle at a given POA.
2. Measure the radial distance from the POA to the outer edge of the 2nd worst shot. This gives you the size of the circle that fully contains 19/20 shots.
3. If this is less than twice the size if your scope click adjustment, you need finer turrets. In the case of a 0.1 Mil turret, you'd be putting 19/20 rounds inside a 0.72" circle (entirely within) at 100y.
​

Now, keep in mind, this 20 shot string is just one sample. For you to really, truly need finer scope turrets, you'd need to do this a few times and consistently best the 0.2 Mil barrier to need finer than 0.1 Mil turrets.



The justification behind the idea above is based on:
1) The assumption that group size is normally (Gaussian) distributed around the POA
2) The well-established idea that 2-sigma values (sigma= SD) correlate to 95% of a distribution
3) The idea that SD is the "average error" for a given shooter/ammo/rifle.



One criticism of this approach is the use of 95% confidence. This is pretty stringent and it means that you are pretty certain the scope here is holding you back.


You may elect instead to use a different confidence. And the group sizing and sample become proportionally much more accommodating to the lower standard. If you choose a 68% confidence (round it to 70%), then you'd only need to put 7/10 rounds inside a circle that is the size of the scope clicks.

Is it tougher to put 7/10 rounds inside 0.36" at 100y or to put 19/20 inside 0.72" at 100y? You be the judge. If you can do either one with consistency, then you might need turrets finer than 0.1 Mil.


You might not be surprised to learn that based on this logic, I will never need a turret finer than 0.1 Mil, and I suspect I'm not alone.

This is a very good statistical analysis of the problem, and I am fairly certain that, mathematically, it is probably true. The issue I have with it is that Shooting, as an art form, involves a good deal more than extrapolation of mathematical concepts (not that you said otherwise).

I suppose my position on the thing may come from a different perspective and opinion, which has always been to center shots and zeroes absolutely as much as I possibly can, to provide margin-of-error for stress, conditions, ammunition/firearm accuracy (or lack), etc.

Everybody that has even a basic level of experience knows that a shooter firing in absence of any stress, at 50 yards, in a protected range, with an accurate rifle will be able to place shots more effectively than they are under any combination of additional stresses on them, or environmental influence on the firearm and/or projectiles. Pretty accepted, and I have never met an exception to that Rule.

So given that tenet, if you have a target that doesn't get bigger with increasing range (say: the 6" needed to reliably impact a deer's heart..or the 2" for their brain), precise centering of zeroes--which is more achievable with finer-graduation adjustments in sighting system--is as critical as it is for the shooter to know their limit and stay within that space when it is live-or-die.

As I said above, there WILL be a cone of fire, regardless of shooter and weapon. If that system produces a cone of fire of 5 MOA, then getting said 5 MOA cone to be well-centered on a 6 MOA target is pretty damned important if you have to HIT that 6 MOA target. The same logic still applies if you are talking about a 1/4 MOA target...or God help you...a 0.100 MOA target.

Now that's my logic for targets that don't get bigger the further you shoot.

In "Target" shooting, it is still a critical worry, particularly if the target is round. The above-discussed cone of fire issue is still a problem on Long Range targets, because obviously, with a Gaussian distribution of shots around the center of your group, if the center of the group is NOT the center of the target, then you will naturally have some impacts fall outside your POA. If the distribution is larger than the "10" ring (whatever target we're shooting), then you WILL drop shots if you don't center. A 1,000 yard X-ring is 10", and the difference in centering between a 1/4 MOA and a 0.1 MIL scope is enough that a really good shooter would drop an X or two for the slack. X-count satisfies ties, and I've lost on X-count myself. (not at 1,000..only 600).

And that's just the statistical distribution issue...

When you throw in the wind's effect on what is mathematically a static--and round--cone-of-fire, you end up with an oblate group along the X-axis. As such, if you do not keep the vertical dispersion of your rifle and handloads (and position...lol!) to a BARE minimum, you will immediately begin losing shots at 2:30, 4:30, 7:30, or 10:30 in even the slightest breeze. The same effect on score will obviously and logically, occur if you cannot (or fail or refuse to) center your group vertically by using your sights.

It was often accepted in "the old days" that 1/2 MOA sights and scopes were "good enough". Rifles and ammunition then got more accurate, Shooters became better and more refined in both goals and performance, and Targets became smaller accordingly. The trend of optics and iron sights toward 1/4 MOA, and even 1/8 MOA in some cases, followed that same evolution of the other parts of the system.

The final piece of evidence, with the recognition that conventional Target people tend to be kinda dogmatic, is that I don't SEE F-Class and experienced Long Range and BR people moving toward Mil. The opposite is probably true for PRS-type shooters, but there's more than one way to make the world go 'round.

At the end of it, it is not my position that 0.1 MIL adjustments will cripple most shooters in most situation, if compared to 1/4 MOA, all else being equal. It IS my position that the difference is more-than-academic for some situations. I own both.

-Nate

 

[Hawkeye7br]

Most shooters, & more important most spotters, don't think in terms of mil. My spotter tells me I'm 3 inches left of center, I can correct. If spotter tells me I'm 8 tenths of mil left, they get beat with a stick. No such thing as having a buddy, wife, kid, etc with binocs or regular spotting scope calling your shot, you still have to convert 3 inches to mil at whatever distance you're shooting. More power to the mil-mil crowd of they can do it. Reality is that most can not.

 

[Hohn]

Nate, dang that was excellent.

One question that occurred to me as I was thinking this through-- how do we ever really know the zero of our rifle? It's really just a theoretical concept of progressively reduced uncertainty. I shoot one shot and of course, it's not exactly at my POA. I shoot another and it's close, but again, not precisely at POA. And let's say I do the improbable and shoot a group that is precisely centered at POA. The problem is that it's just one group. Will the next be exactly POA? Probably not. I can shoot several 5 shot groups. Each of them will have a slightly different center. Which of them is the "true" zero? Is is the center of the centers, like a meta-group?

If I shoot enough groups under controlled conditions, each group becomes a sample that it telling me more about the actual population of all shots. And in so doing, I can come to know the distribution of those shots and slash the uncertainty about the center of those samples to where I can no longer detect the error in my zero. But that's not eliminating the error-- it's still there. It's just so small I can't detect it, and it's no longer significant compared to my turret increment and--more likely-- shooter ability and application/environment conditions.


Thus, the only partial rebuttal I could offer to your practical desire for the finest possible turret adjustment is that you'd have to have a very accurate rifle to even know where the zero is with enough confidence that your turret adjustments are correct. What is the relationship between the confidence in our zero and the rifle's accuracy?

The turret adjustments are discrete. The shot distribution is continuous/analog. The process of zeroing forces us to choose between neighboring clicks.

Since wind has more variation, let's just focus on elevation and Y-axis for a thought experiment.


I shoot a sample, 10 shots and 7 of them are within a 1 MOA diameter circle. This sample size and group size point to a standard deviation of plus or minus a half MOA (either side of center). If I had placed 19/20 inside that same 1 MOA circle, then the SD would be 1/4 MOA. But since we only got 7/10 in the 1MOA ring, our SD is 1/2 MOA.

Summarizing for clarity: A rifle that will put 7/10 shots inside a 1 MOA circle has a SD of half MOA.

What does this mean in terms of having 1/4 MOA turrets?

Well, it means I have to choose which of these distributions better fits my group:

Not so easy with all that overlap. If you do the math, you find that about 37.5% of the area of one curve is under the other curve also. In other words, you have only a 62.5% chance of choosing the "better" zero because so many of the points you shoot will fit in either that scope click or the one next to it.

Now let's say I have a rifle that's twice as accurate --7/10 shots within a a half MOA circle, giving an SD of 1/4 MOA.

Now my 1/4 MOA scope clicks force me to choose which of these is a better fit:

Still an amount of overlap that is not insignificant. If you calculate the area in the middle triangle, you'll come up with about 31%. In other words IF you have a rifle that shoots SD= half-MOA, there's still a 31% chance that you'd be "blind" to the difference between two possible vertical zeros with 1/4 MOA clicks. Conversely, whichever zero you pick is only about 69% chance of being right.

What if I have an amazing rifle and load that is SD= 1/3rd MOA? How much are 1/4 MOA turrets holding me back?

Now the overlap of the distributions is only 22.78%


You get the idea. If you do the math for a 1/8 MOA SD rifle with 1/4 MOA turrets, you'll discover that the overlap between the two closest possible zeros is 14.7%.


A rifle that can put 19/20 inside a 1 MOA circle would have a +/- a quarter MOA SD. And any rifle with SD equal to the scope's turret increment can never be zeroed with more than 69% confidence.


Why show all these examples with the 1/4 MOA turrets? Because they show just how low the confidence in a given zero really can be, even with a pretty accurate rifle.

Finer scope adjustments make the problem worse, not better.

Let's go back our example of the rifle that has SD= 1/4 MOA. With the 1/4 MOA turrets, the overlap between one click and the next is 31%. But when the clicks are closer together, the overlap is 37.48%, making it even harder to distinguish one zero from the other.

I'm willing to bet a lot of people with the really fine turrets end up chasing zeros a lot.

 

[natdscott]

One question that occurred to me as I was thinking this through-- how do we ever really know the zero of our rifle?

Which of them is the "true" zero? Is is the center of the centers, like a meta-group?

Zeroes are flexible. A common idiom in Long Range is "Zeroes are plus or minus a minute at 1,000."

I call my "zero" on easily-adjusted and recorded sighting systems the resulting zero from multiple days and weeks and months of shooting it at KD. Is it still +/- a little? Sure.

Knowing the differences that make it +0.5 MOA, or maybe -0.4 MIL on a given day or condition is one thing that makes an accomplished shooter with an accomplished rifle.

But here's this: when I zero a set of FIXED irons, whether it is my rifle or somebody else's, I take it really slow and easy, because I am very serious about centering the zero, but you can't put metal back on.I'll shoot enough rounds on a day under some specific condition and get the sights pretty close to centered...then I'll clean the rifle and put it way. After waiting for a different condition (if possible) such as colder/hotter/etc. or even drastically different humidity, I'll go shoot another set of "zeroes". If you do this a few times, and under varied conditions, and save the targets for measurement and adjustments of the METAL, you are going to get as close to centered a "general" zero as possible with that sorta sight, with the least damage possible. From there, you leave it alone, and it's on the shooter to figure out how to hold off, etc. to make hits when conditions dictate something other than POA/POI.

That's a meta-group approach, I think.

What is the relationship between the confidence in our zero and the rifle's accuracy?

Oh, probably there's a tie there. I have some very accurate rifles, after a little practice and some time spent with tools and measuring equipment on the rifle itself. It's true that I feel better about the zeroes on the more accurate rifles, and when I am on the gun, I'm within a "click" either way of hitting damn near anything I want to hit, provided I call the wind straight. And that's a big "provided".

As I said before, for single shots in field conditions, I'm pretty sure I can't tell the difference between an exactly-centered zero, and one that is off by ~0.08 MOA.

Finer scope adjustments make the problem worse, not better.

I'm willing to bet a lot of people with the really fine turrets end up chasing zeros a lot.

Can't say. I don't have any scopes or sights with 1/8 MOA. I do know that I've had to hold off with 1/4 Clicks before though. Take a look at the dimensions of the UIT 50m target. It's hard to get most of your 0.210" holes in the middle.

Ok...metric. Let's look at the 300m target. It has a 10 centimeter 10-ring. By my math, that's 1/3 Mil at 300 meters, and even in Prone, the best shooters are hard, HARD pressed to hold 1/2 MOA (or ~0.133 MIL, if you prefer) in the absence of any wind...which would already be a cone of fire of almost 4.2 cm. Mere mortals like myself are probably shooting more like 6-8 cm as it is...

...but in this example, even with a 1/2 Minute rifle and shooter, you have less than ONE 0.1 MIL click either direction from a hopefully-centered zero before you start dropping nines. This, compared to a 1/4 Minute sight that would at least give you a choice, albeit a tough one.

Most of the sights used in these metric games are "Twenty Click", which moves bullet impact 0.024 MIL, and the finest sights I am aware of move the impact only 0.010 MIL per click.

That's done for a reason, and my first post about "Tenth Mil will getcha killed" was, however abrasive, directed at this fact.

The advent of 0.05 MIL scopes for target use is also an indicator that somebody somewhere in the scope market thinks 0.1 MIL can be too heavy.



I will totally capitulate that that level of shooting does not in any way represent "most shooters", "most rifles", or "most targets". Trying to use a sling rifle to keep all your shots in the bottom of a coke can at well over 300 yards is not many people's idea of a good time.




What I will say about the shooter end of the problem is that they need to have the confidence and knowledge to know when to turn the knobs, and when to leave well enough the F alone, and just focus on the crosshair and trigger.

Lack of ability to resist chasing zeroes is not a valid reason to accept a coarser sighting system than is truly necessary for the targets at hand.




Some of both of our points are probably pretty academic, and we'll probably have to agree to disagree, even though I own both systems, but I hope that maybe this thread is providing some thought and/or enjoyment to somebody other than ourselves.

-Nate

 

[rhino]

Basically using either 1/4MOA or 1/10th MIL at any distance the 1/4MOA is going to be the smaller unit of measurement if I understand it correctly.

Yes, because the angle = 1/4 MOA is smaller than the angle = 0.1 MIL.

 

[rhino]

Most shooters, & more important most spotters, don't think in terms of mil. My spotter tells me I'm 3 inches left of center, I can correct. If spotter tells me I'm 8 tenths of mil left, they get beat with a stick. No such thing as having a buddy, wife, kid, etc with binocs or regular spotting scope calling your shot, you still have to convert 3 inches to mil at whatever distance you're shooting. More power to the mil-mil crowd of they can do it. Reality is that most can not.

And rightly so. It's like "Super Troopers" when Officer Farva orders a "liter o' cola."

 

[Hohn]

Nate, thank you for your thoughtful postings here. Exploring pro and con arguments is how I tend to increase my understanding, but I know that it can be taxing if someone thinks I'm arguing with them rather than just exploring an argument in greater detail.

You and I couldn't be farther apart in real world experience-- I've never shot a match. So I readily confess that my analysis here is based on grasping at theory and trying to understand.

 

[Gabriel]

Most shooters, & more important most spotters, don't think in terms of mil. My spotter tells me I'm 3 inches left of center, I can correct. If spotter tells me I'm 8 tenths of mil left, they get beat with a stick. No such thing as having a buddy, wife, kid, etc with binocs or regular spotting scope calling your shot, you still have to convert 3 inches to mil at whatever distance you're shooting. More power to the mil-mil crowd of they can do it. Reality is that most can not.

My spotter and I (or the other way around depending on who is on the rifle) have the eternal war between MIL/MOA. He is all MIL (even though he has a MK4 on his rifle that is MIL/MOA) and I'm all MOA (even though my work rifle has MK4 for that is the same as his). I'll spot and tell him his correction in MIL, he does the math and corrects... yet he acts like I'm speaking a foriegn language if I just tell him he's three inches right. I don't get it. The damn turrets are in MOA. If he gives me a correction in MIL, he gets an ear full.

Truthfully, it's easy enough to spot for him with a spotter with MIL reticle and vice versa. It could probably be more convenient if he just pulled his head out of his ass and went with MOA.

 

[tradertator]

Mils are not metric, and MOA is not US standard. Both are simply methods to measure an angle (in this example, the shooters line of sight to the target vs the curve of the bullet). It just happens to be that at 100 hundred yards, 1MOA is approximately 1". The same is true for .3 mils at 100 yards. Rather than thinking in IPHY (inches per hundred yards), think of either unit as a way to measure the angle of your bullets arc, and it will help demystify long range shooting (as least in my experience). Either is fine as long as you know the dope on what you are shooting.