Black Rifles & Tactical Guns

Real World Knowledge: How To Range A Target Using MOA

REUTERS/Oleg Popov

Guns and Gear Contributor

By Eric Patton, RangeFinder.com

There are many arts that are becoming lost to technology and this is a shame for so many reasons.  Just like people are going to GPS devices to replace a compass, too many shooters are relying on their laser rangefinders rather than learning the basics of ranging with a reticle.  Eventually that rangefinder will fail and your shot will become impossible.

To this end, we need to discuss ranging and how it is done using nothing more than your scope and a little knowledge.  This is one case where you don’t even need experience as long as you have a good premise to start with.

The Scope

Before you start, you need a scope capable of doing the tasks required.  For that, there are many scopes but this article outlines a few that are a good bet starting out.  Which brand and model scope you have isn’t that important as long as you know a few things about it.

The first thing you have to have is a reticle that has measured markings.  These are usually either Mil or MOA.  The basic system for using each is the same but we are going to focus on MOA for this article.  There are resources that can explain the different equations.  You just need to know which measurement you have.

We are using MOA here because I feel it’s the easiest to use overall and it’s my preferred system.  No other reason.

Once you know your system, you need to make sure you are getting an accurate measurement through your scope.  To do this, you need to first know if your scope uses a first or second focal plane.  This is where most people go wrong.  If your scope is not variable powered, this is a moot point and you can skip it.

A first focal plane will have a reticle that changes size as you increase or decrease magnification.  This means that the measurement in MOA will always be the same no matter what.  A first focal plane scope makes things more streamlined but it’s not a necessity.

If you have a second focal plane scope, the reticle will not change size.  This means that measurements taken through the scope will differ depending on what level of magnification you are at.  In this case, you will need to find out the magnification in which the scope has an accurate measurement.  This is usually the max magnification but check your documentation or contact the manufacturer to be sure.

That ends everything about the scope that is important.  The only thing left is the knowledge you need to get it right.

The Basis

For this, let’s say there are three things that you can know about a target:

  • You can know the height of the target in real-world measurements. I usually use inches as the math is easier.
  • You can know the height of a target using your scope measurements. As stated above, this is in MOA for this article.
  • You can know the distance to the target. Sticking with imperial measurements, I use yards but you can easily use metric measurements if needed.

As long as you know two of these things, you can figure out the final one with a simple equation.  Often you will not ‘Know’ these things but have to estimate at some point.  The closer you estimate, the better the end result will be.

The Process

Now is where we come into a little math but we will keep it easy.  Keeping a small calculator around is a good idea.  Not only does it remove human error but its often much faster than relying on your brain.  Sometimes in the baking sun, lying prone for a shot my brain doesn’t like math as much.

To explain this better, we are going to use a real-world example of a deer hunter after a good-sized buck.  This will make the math mean something.

Using our three points above, we are going to be able to measure the buck in MOA through our scope.  Most scopes don’t have single MOA marks.  We will have to get as close as we can.  Since the scope I use has markings for every 10 MOA, we will say the deer is just over 1 of these marks high but less than 1 and a half markings high.  We estimate the deer is about 12 MOA high at the shoulder.

For a male deer at the shoulder, they are often between 2.75 and 3.25 feet where I live.  We have to have a number here so I usually use 3 feet as a good solid estimate.  That is 36 inches.

We now have two of the three things we can know about a target.  That is sufficient to find a solution for the third point.  We will use this equation to figure that out:

Range in Yards = Height in Inches / Height in MOA * 95.5

The final number there is a correlating value that depends on the measurement system you use for the height of the target.  If you want the range in meters, the number is instead 87.3.

For us the equation will look like this:

Range in Yards = 36/12*95.5

Or solved a little further:

Range in Yards = 3*95.5.

You can do this using a calculator but it’s not that difficult to do in your head.  The range to our3-foot tall deer is 286.5 yards.

The Art Of Estimating

Sometimes as hunters we need to make our shots a little faster.  Sometimes we don’t have the time to rely on a calculator so we simply things to get ‘close enough’ on our range to make an accurate shot.  For our example above, how accurate do we need to be?

I often hunt with a .300 Winchester Magnum.  The difference of 15 or 20 yards at the range our deer is will not drastically affect my shot.  I may be a quarter of an inch off but that is going to have zero effect on my chance of a kill.

For this I will often go through a mental exercise rather than break things down to the equation.  The deer is about 36 inches tall and measures 12 MOA.  Divide that out and you get 3.  Multiply this by 100 which is close enough to 95.5 and I get 300 yards.  From there I am ready to dial in my scope and take my shot.  It takes only seconds.  I can do that faster than you can get a reading on a laser rangefinder.

Experience always comes into play at some point and estimating is that point.  The more variables you introduce into the system, the more likely an error is to occur.  If you do not have a good idea of the height of your target in inches or if you get the MOA measurement off, that can be a miss.  Use the formula as written until you become comfortable with how it works for you.  Then try estimating.

Your caliber and the total range of the target can also mean a need for greater precision.  At 300 yards, my .300 Win Mag won’t have a drastic difference in point of impact if I am off by 20 or 30 yards.  At 800 yards, it’s fussier.  If you use a caliber like a 5.56mm, that 20 yards is a lot more of a variation since you have a more pronounced bullet drop at 300 yards.  In both of these situations, you need greater precision in your calculations.

The DOPE Chart:  Making Range Mean Something

Once you know your range, you have to make it work for you.  This is where the DOPE chart comes in.  For those that don’t know, DOPE is an acronym for Data On Previous Engagements.  This is how you dial your rifle in to make that hit.  It is just one more way of reducing your chances of error when the pressure is on.

A DOPE chart will tell you how far your bullet will drop at different ranges and how to adjust your scope to make it align with the target just where you want to hit.  Despite the nomenclature using previous engagements you can actually do this very easily, especially for production bullets.  Sometimes you can even download one straight from another shooter and it will work for you.

Bullet Drop depends on a number of factors and is more complicated than what we need to get into here but at its core, it’s bullet velocity and bullet weight that make the most difference.  As long as you have a production bullet and know your barrel length, everything you need is already there.

Always use the same bullets so you know these variables and never use the same DOPE for a different rifle or bullet.  My typical hunting round is a 178 Grain Hornady round and we can apply that to our above example.

Our deer is roughly 300 yards downrange.  I check my dope chart and see my bullet drop for that range is 3.2 inches.  This comes from factory calculations or data on previous shots.  For my scope, that is about a single MOA of adjustment using my turrets that are 1/4 MOA per click.  Simply adjust to the positive elevation 4 clicks and I am dead on target.

Considering the low bullet drop, I would probably just take the shot from where I was because bullet drop is so negligible but your caliber, range, and experience will be your guide here.  That said, I would be very confident with this shot and a positive hit.  With a good expanding .300 win mag hit, that deer is going down.

Conclusion

Long-range shooting can get tricky.  There are a lot of variables that need to be ironed out and a lot of practice before you can get right on target.  Some aspects are very challenging and take hundreds of rounds of practice before you get them down.  Of these, range estimation is probably the easiest.  Don’t let this stand in your way.  Practice it so when your technology fails, you have the knowledge to fall back on.

Eric Patton has been an avid shooter in many disciplines over the years but took to the long-range shooting and hunting game about 20 years ago.  Though he strives to push ranges farther than his current record, his longest hit on a target was 981 yards with a .300 Win Mag built by Bergara.  His longest hunting kill was a whitetail deer taken at 714 yards with that same rifle during the fall of 2018. You can find more articles from him on https://rangefindertoday.com