This is not a basic guide. I will not be discussing basic weapon operation. This guide is aimed at players who already know at least the basics of sniper rifle operation, ranging methods and so on.

This guide is for players who play sniping roles and use the mil dot scopes frequently.

NOTE: for a completelly tl;dr experience, just read the bottom of this section and jump right into the charts.

It is not uncommon for a sniper unit to support an infantry assault, or any similar operation. In these situations the sniper and assault team will probably engage a group of hostiles simultaneously. However, the sniper will probably be far away from the action.

After correct assessment of the range to the targets and zeroing the scope, there are two issues that come up when the time comes to aim and pull the trigger:

1. the zeroing works on steps of 100m, and targets rarely stand at exact multiples of 100m from the sniper;
   
   
2. targets are rarely alone, and they tend to not stand shoulder to shoulder at the same range from the sniper. It is not unnusual for targets to be dispersed as far as 50m from each other, and re-ranging/re-zeroing for each target is rarely an option;

This means that aiming will not necessarily mean using the center mil dot. If you are engaging a target at 850m, you need to adjust the aim. If you are engaging a group of targets dispersed at ranges that differ by tens of meters, you will need to use different mil dots to engage each one.

The issue is, this adjustment is not a constant proportion. Bullets drop due to gravity. The speed at witch they drop is constantly increasing. When this ever-increasing speed combines with an ever-decreasing bullet speed, things get tricky, especially for the 12.7mm bullet, which is significantly affected by air resistance.

I decided to analyze the behavior of sniper rounds at different distances. When you're aiming at a range between 400m and 900m, adding 50m of range on the fly could be as simple as aiming half-way down one mil dot, but all calibers are different.

I decided to position myself at certain distances from static targets, and zero my scope to a "wrong" range, and write down what adjustments each situation required.

I came up with a lot of data. Many guides mention "getting a feel for it", but when you are engaging a target at over 900m, it is often near impossible to know where your shots are landing in order to readjust. Having a reliable initial reference should help a lot, so I decided to share my findings here.

Some people will probably think these charts are highly unnecessary. However I disagree, especially when taking into account the drop rates for 12.7mm.


tl;dr:

The following tables work like this: for a set scope zeroing, what adjustment can be made on the fly to take aim at a target at plus or minus 100m from that zero? This is useful for both aiming at targets that are not at a range divisible by 100, and to progress through different targets within a group without re-ranging and re-zeroing. Do NOT use values beyond the 100m represented here by simply multiplying. Always work within these 100m groupings. This has to do with the way the zeroing mechanic in Arma emulates the real world complex math of zeroing.

Section regarding calculating for elevation differences after the tables.

The Marksmen and Apex DLCs added a bunch of new weapons, firing a wide variety of calibers.

The MAR-10 with its precise high-speed .338 rounds is a viable option at long ranges, lagging slightly behind the M320. The Cyrus fires a 9,3x64 round which is bigger yet a bit slower than the .338. This means it has slightly more stopping power at medium ranges, while losing its effectiveness beyond 1200/1300m.

For these reasons I've included the MAR-10 on this guide, and am considering including the Cyrus.

The rest of the rifles are not capable of being used at these sort of ranges as reliably, so I featured them on my new designated marksman rifle guide.

The MAR-10 is classified as a marksman rifle.
However, it is perfectly possible to employ it for either role. I have verified the rifle's ability to place good groupings on human sized targets up to 1700m (might be capable of more, but I stopped there).

The steepness of the terminal trajectory at ranges above ~1500m may be an issue, as it greatly amplifies any imperfection that occurs during firing, given the much smaller cross-sectional area the target presents to the incoming projectile.

From what I can tell, this caliber goes through most body armors with relative ease at medium range. You shouldn't need more than a single shot. Beefy body armor may need two shots.

It is also essential to keep in mind the fact that this rifle may be equipped with a suppressor. Doing so alters the ballistic behaviour of the projectile, given how the practical length of the barrel is increased.


Here is the milliradian adjustment table for the Mar-10:

(!) In the LRPS there are only 4 mil dots on each side of the center dot. The end of the spacing after the fourth dot can be considered a fifth dot, and with some intuition, the placing of a theoretical sixth dot can be guessed. I do not advise doing so, though, given the increased uncertainty involved.

Examples:

• unsuppressed and zeroed for 600m, to hit a target at 650m, I need to aim three quarters of a mil dot below center;
  
  
• suppressed and zeroed for 1200m, to hit a target at 1300m, I need to aim using half a mil dot above center;

An extremelly efficient caliber with good penetrating power and a very high ballistic coefficient.
This makes it lose less velocity over time, which reduces the overall bullet drop, meaning adjustments are never too big.


Examples:

• if I have the scope zeroed for 700m and I want to hit a target I know to be at about 600m, I aim using one mil dot above the center dot;
  
  
• if I have the scope zeroed for 1000m and I want to hit a target I know to be at about 1050m, I aim 0,75 mil dot below center dot (so 3/4 of the way to the mil dot below);

This caliber is a pain in the ass. It weighs twice as much as the .408, and travels only slightly slower, which means it packs quite a punch, but the rate at witch it descends (due to combination of drag and gravity) is huge. The adjustments beyond 1000m get a bit silly.

(!) In the LRPS there are only 4 mil dots on each side of the center dot. The end of the spacing after the fourth dot can be considered a fifth dot, and with some intuition, the placing of a theoretical sixth dot can be guessed. I do not advise doing so, though, given the invreased uncertainty involved.

For this caliber, above ranges of 1200m correct zeroing is imperative, and adjustments for even a few tens of meters become huge. That's the downside of the Arma zeroing mechanic, with its 100m increments.

Examples:

• zeroed for 600m, to hit a target at 650m, I need to aim using one mil dot below center;
  
  
• zeroed for 1200m, to hit a target at 1225m, I need to aim using one mil dot below center;

Armor Piercing Discarding Sabot.

Being a sabot round, the bullet is actually smaller than the standard caliber, and is encased in a sleeve that falls off after the projectile exits the barrel. The smaller bullet is made of a denser metal, which means the loss in mass is not directly proportional to the loss in volume, which allows this smaller bullet to still retain a very high percentage of the total muzzle energy of a standard 12.7mm round.

This high-speed + small heavy bullet formula makes for a projectile that is much less susceptible to air resistance, which means it does not deccelerate so fast, which means it does not drop near as much as the standard 12.7mm round with its silly 4 milliradian and higher adjustments.


Examples:

• zeroed at 800m, to hit a target at 850m, aim 0,375 mil dot below center;
  
  
• zeroed at 1100m, to hit a target at 1000m, aim 0,75 mildot above center;

This caliber is very neat. It's very fast, and doesn't drop much more than one mil dot at any of the ranges I tested. It also penetrates like crazy (aprox. 175% the already impressive penetrating power of the standard 12.7x108mm round).

It is very tricky to engage moving targets, especially beyond 600m, but that is not the only use for this information.

It's important to remember that, should the target move even a single meter to the side while the bullet is in flight, the shot is probably ruined, and the target is now alerted to your presence. Being able to analise the target's behavior and having the intuition to predict whether he is likely to move during the flight time window is important, and to assist in making that judgment, a rough knowledge of flight times for the different calibers comes in very handy.

This is rarely discussed, but it is important in some situations. When you are plotting a firing solution, you need to take into account elevation changes, especially at longer ranges, when corrections for small range deviations become larger.

Estimating your angle is hard to do without a laser designator. Rangefinders do not evaluate angle. In that case, if you have time to, try using the map. Find the elevation under you and the target area, and simply use the standard Pythagorean theorem to find the real range.





Depending on which elevation is bigger:


(the subtraction under the square root should be ordered in a way that allows for a positive value result)

example:

your elevation is 250m
target elevation is 100m
measured distance is 1200m

realRange=sqrt( (1200^2)-(150^2) )
realRange=1190m



If you have a laser designator, all you need to do is a trigonometry calculation.



The purple angles are the same, so you basically know that the true range (adjacent side) will be equal to the measured range (hypotenuse) times the cosine of the angle.


here's an example:

you are on top of a tall cliff, overlooking your target
your designator indicates a range of 900m, and an angle of 20 degrees

realRange = 900 x cos(20)

realRange = 846m (aprox.)

That's a difference of over 50 meters, which often means you wouldn't hit the target had you not calculated the real range.

You should always zero your scope according to the calculated real value, since that's the distance over witch gravity will be influencing the bullet.


Here is a quick reference chart for interpreting angle readings on the fly:


This means 1000m could become 900m, and 600m could become 540m, depending on the angle.


For a given elevation difference, this effect diminishes for longer ranges, but it's still there. Don't forget about it. Especially since at those longer ranges, aiming with the 12.7 standard round, for example, means an adjustment for 25m could be over a mil dot in correction.
For closer ranges (~300), only very steep angles really affect the ranging (>30°), but if you're sniping and a hostile is that close to you, you have more important things to worry about than angles and stuff.

I have never in my life held a real firearm in my hands. My ballistics knowledge is limited to the physics involved and my experience in videogames. Those are mostly the S.T.A.L.K.E.R. and Sniper Elite series, plus Arma 3. Counter-Strike doesn't count, as it uses "lasers" instead of ballistics.

Therefore, if you find any wrong value in this guide PLEASE let me know, I will correct it and credit you.

I did not measure adjustment requirements beyond ranges of 1400-1500m because I don't believe actual Arma 3 gameplay involves a lot of >1500m firefights;

For the 12,7mm caliber I wouldn't have done it anyway. (silly >5 mil dot adjustments)

If anyone is interested in doing so, feel free to report the readings you get, I'd be glad to add them to the tables and credit you.


I made a guide on mil-dot adjustments for designated marksman rifles. You can find it here.


I did the bullet flying time measurements and redid all three mildot adjustment sections using the "Lupus' Training Grounds Version 1" scenario (by Lupus). It uses the same dried lake as the "Weapon damage and vest protect" scenario by the same author, but this one also spawns static targets and vehicles.

The image in the intro section is an aglomeration of images of the real-life rifles that inspired the Arma 3 rifles. First one is the Gepárd GM-6 Lynx and the second one is the CheyTac Intervention M200. The third one is tricky. The MAR-10 is supposedly inspired by the Noreen “Bad news” 338, and while this might be true for the ballistics, the outer design is actually inspired by the Salient Arms International SAI-T2, a variant of the AR 15. Since there's no real life counterpart to the MAR-10, I used some official artwork from Bohemia. The first two rifles are to scale relative to each other.

I hope you enjoyed this guide. I have improved on it as much as I intended to, and I consider it a finished project. However, if you think something could be added to the guide to make it better, feel free to suggest (sniper rifles/scopes/calibers related only).

Deimos F