Rifle 101: Sighting In
Thinking back on my now ten years of recreational shooting and thirteen years of firearm collecting, I’m often amazed by how far I’ve come and how much I’ve learned. Having grown up in a decidedly not-pro-gun house, I came into the firearms community as a blank slate with no prior experience. I did have enough humility to realize that I needed to learn the basics from someone who knew what they were talking about.
Scouring the internet as a firearms neophyte led me to discover plenty of trainers and training organizations – some much better than others – but I lacked the requisite knowledge at the time to sort the good from the bad. More importantly, if I simply wanted to read about a specific issue or training topic, relevant information was spread all over the place. Sometimes great tutorials could be found on one of the thousands of firearms message boards scattered across the web. Other times, YouTube videos were helpful in explaining issues. On other occasions still, online magazine articles and blogs carried the best information.
This column is intended to address some of that information balkanization. I will explore a collection of novice-to-intermediate level firearms issues and questions. Topics that are either exceedingly common or have perplexed me as I’ve grown in the firearms world.
Let’s take a close look at a handful of related topics that can best be summarized as “zeroing” your rifle. It’s a process that experienced shooters find easy but dreadfully unexciting. For newcomers who may not be particularly accurate shots, to begin with, it can be a real challenge. That’s why this article starts from ground level and builds from there.
Mind Your MOA
It’s virtually impossible to grasp how to dial-in a sight if you don’t first understand minutes of arc, or MOA. You’ll sometimes see this termed “minutes of angle”, but “arc” is the correct nomenclature. Technicalities aside, the two mean the same thing.
Conceptually, MOA is simple. A single rotation of the dial can be subdivided into 360 degrees. Arcminutes take these full degrees and divide them into 60 smaller sections for even greater precision. Thus, a full rotation is 60 times 360, or 21,600 arc minutes.
Now, let’s apply arc minutes to shooting at the range. Imagine for a moment that your target rests somewhere along the circumference of an imaginary circle and your shooting bench sits precisely in the center. Your origin, or zero, is a line directly from you to the 10-ring on the target. Likewise, aiming 21,600 divided by 2, or 10,800 arc minutes off-target would result in your firearm being pointed directly behind you. Aiming 5,400 arc minutes up would be straight up. I think you’re starting to get the picture.
Obviously, you never hear anyone talking about their rifles shooting thousands of MOA off-target. That would be absurd and at that point, we may as well measure dispersion in terms of full degrees. The reason minutes of arc play such a significant role is the way the measurement conveniently lends itself to a typical 100-yard range, which we can think of as a circle with a radius of 100 yards.
At this range, the linear distance between point A and point (A + 1 MOA) is 1.047 inches. Rounding this to 1 inch allows us to keep the math simple – at 100 yards, one MOA equals 1 inch. Pretty neat, right? What’s really remarkable is when we talk about 1 MOA accuracy, we’re talking about a rifle/shooter combination is capable of keeping every round within 1/60 of one degree, edge-to-edge – or 1/120 of one degree from the center of the group.
The beauty of this relationship is that it scales linearly. A single MOA at 200 yards? You guessed it, 2 inches. What about at 25 yards? There, 1 MOA is just 0.25 inches. As we move to longer ranges, that 0.047-inch rounding error will start to gain significance. However, for most shooters – even those who practice frequently – aren’t consistent enough for this to matter. And even at 1,000 yards, the error is still less than 0.5 inches. To make matters worse (or better?), the adjustments on most scopes and red dots are actually calibrated for rounded MOA, sometimes called Shooter’s MOA.
Start Small
One of the first mistakes new shooters make when trying to zero a rifle is to immediately aim – literally – for 100 or more yards. While that distance (or further) may be the eventual goal, it is important to “get on paper” before becoming too ambitious. Otherwise, there’s a good chance that a lot of ammunition will go to waste.
Put simply, “getting on paper” is the process of ensuring that the rifle’s point of aim (POA) is in the correct vicinity of its point of impact (POI). Particularly with new rifles or ones that have recently received new optics, it isn’t uncommon for the POA to be so far off the POI that hitting a sheet of paper at 100 yards is neigh impossible. For this reason, it’s always a good idea to start your efforts at a much shorter range – 25 yards if possible, but no more than 50 if circumstances dictate pushing the target out a bit.
The idea here is simple. Remember our MOA discussion just a moment ago? For the sake of discussion, EOTech holographic sights feature a whopping 80 MOA of adjustment range. 40 MOA on each side of the center and on both axis. That means that in a worst-case scenario the POA could be off by as many as 40 inches in any direction at 100 yards! It’s highly unlikely that any optic would arrive at the very end of its adjustment range. But for example, a fully-functional EOTech could have your rounds anywhere inside an 80×80” area at 100-yards. For a sense of scale, that’s nearly 10 pieces of letter-sized printer paper in width!
Moving closer, to 25 yards, divides that range by four. Now, the adjustment range from the center is just 10 inches in any direction. Considering the improbability that an optic would come fresh out of the box at either end of its adjustment range. There’s a very good chance that the first few rounds will land somewhere on the paper.
Consistency is Key
So you’ve managed to get your rounds to land at least somewhere on the target. The next step is shooting our first groups. The term group refers to a collection of rounds fired using the same POA. Since adjusting to each individual round wouldn’t properly account for mechanical and user-induced variance, we use groups to determine a good average POI. The integrity of each group is critical to proper zeroing. Therefore, it is crucial to maintain as consistent a POA as possible for each shot. More importantly, don’t get impatient. Your rounds shouldn’t be landing on target at this point (unless you’re fortunate to have a perfectly adjusted sight out of the box), so don’t try to swing some “Kentucky windage” hoping to land them in the 10-ring. You should also stick with a single ammo brand and loading (the one you plan to use frequently) throughout this process.
Don’t Overdo it… or Underdo It
The ideal number of rounds for each test group is a subject of some debate. Firing too few will provide insufficient samples to accurately determine your offset. Too many and you invite flyers or user-induced outliers that skew your results. Keep the number of rounds per group to no fewer than three and no more than ten. There may be some shooters with extraordinary accuracy requirements who deviate from these recommendations, but this should cover most situations. Personally, I like to stick with three to five rounds per group. Three early on just to get close and then five when I need to dial things in more precisely. Once you’ve fired your group, measured, and adjusted your sights accordingly, continue to repeat the test until your POA and POI are aligned.
Setting Your Sights
If you have a magnified optic or red dot, adjusting the POA is going to be very easy. This is partly because of the simple-to-use dials for windage (left and right) and elevation (up and down) adjustments, but it’s also thanks to the straightforward way they go about addressing POA changes. Generally, optics ask you to “move” the POI to the POA. Example: if your rounds land too low you need to turn the elevation dial in the “up” direction to “move” the rounds up to your POA. Likewise, if your rounds land left of center, dial “right” to shift the POI toward your aiming point. A click of the turret dials on most optics equals ¼ to ½ MOA of adjustment but be sure to check the sight’s manual for the exact value.
Iron sight adjustments can be a little more challenging to visualize, not the least of which is because the process to set them varies wildly from firearm to firearm. If the rifle’s front sight is the primary point of adjustment, as is the case with AK variants, your approach to getting on target will vary greatly from adjusting a western rifle, like an M1 Garand, an M14/M1A, or even an AR-style rifle where front sight adjustments are limited or non-existent and most changes are made at the rear. And yes, I realize most AR front sights offer front-adjustable elevation.
If your rifle’s front sight is where your tweaks must occur, things will seem backward. If your rounds are landing right of your target, you need to float the front sight post right as well. This will have the effect of moving the barrel left in relation to your sight plane. Thus the POI will also make a leftward migration. Front sight elevation changes work the same way. If you’re hitting high, move the post up to shift the sight plane up.
Moving back to the rear sight means mirroring the advice just given. In this case, a POI to the right of the target requires drifting the rear sight left. A POI above the target is cause for lowering the rear sight.
Even after a decade of shooting, I frequently need to sit and think these situations through.
Wrapping Up
At this point, we’ve covered most of the key bases in getting a rifle on target. There are several advanced topics under this umbrella that I hope to cover in later pieces, namely concepts like battle zeros and ideal zeroing ranges for specific calibers/firearms, but without the building blocks laid here delving into those topics would not be supported by a sufficient foundation.
An information security professional by day and gun blogger by night, Nathan started his firearms journey at 16 years old as a collector of C&R rifles. These days, you’re likely to find him shooting something a bit more modern – and usually equipped with a suppressor – but his passion for firearms with military heritage has never waned. Over the last five years, Nathan has written about a variety of firearms topics, including Second Amendment politics and gun and gear reviews. When he isn’t shooting or writing, Nathan nerds out over computers, 3D printing, and Star Wars.