Zeroing my AR: How Far is Best?
The trusty ol’ M4 zero sheet
I’ve punched my fair share of holes through this paper, and pretty much any Army veteran has. You’d set it up at 25 meters and launch green tip 5.56mm rounds into the circle, then you made your way to the qualification range confident that your zero would work exactly the same at 300 meters as it just had on the close targets.
And it was true. Plenty of folks knocked back that 300 meter silhouette with confidence after a short range zero. What many of us didn’t really know at the time was the method behind the madness. Or the science. Why didn’t we zero at 50 meters, or 100? Of course, we practiced with the ammo we fought with, so concerns of ballistic differences between practice and duty ammo didn’t exist.
Up until the very moment I started this article, my AR builds were zeroed at 25 yards. Why? No reason other than that is what I always knew. I knew my hold unders and hold overs from practice and called it “good to go.” However, as I began to consider my fighting rifle build, the more I wondered if that was the right choice for my intended ranges. My defensive carbine is a 200 yard rifle at most, 100 yard rifle most realistically. I live in a built up area where MOUT and CQB are far more pertinent disciplines than ranging and pure marksmanship. I use iron sights or red dots. So why was I zeroed for a hypothetical 300 meter shot?
With the help of the JBM Ballistic Calculator I began doing some numbers crunching and came to some interesting conclusions.
Real quick, let’s define the Battle Sight Zero. Simply, it is the sight settings placed on your rifle for combat. On a fighting rifle, you aren’t going to be adjusting your elevation settings on the fly to hit targets at different distances. The way around this is to zero your rifle at a known distance and then commit to memory how far below or above that point of aim your round may hit at other distances.
Out of the barrel, rounds will rise. As gravity takes hold and they lose momentum they will fall at an exponential rate. The other thing to account for is how tall your sights are over the bore of the rifle. This is why rounds hit low when you shoot at a 7 yard target on an indoor range. The round trajectory is also why your rounds hit tall on the 50 yard range after zeroing at 25 yards.
The goal of this article is to find out which BSZ distance is the most useful.
For this test I selected the Federal Premium American Eagle M193 5.56 NATO 55gr round. I did this for a few reasons, but the main one being availability and pertinence. It’s available and affordable, and something almost all of us have shot. It’s a popular practice round, in addition to what most folks will buy in bulk to load their mags with. I hoped that the resulting numbers would be most accurate to what the majority of our readers would have in their gun cabinets. I set the velocity to the advertised 3,100fps from a 16″ barrel.
25 Yard Zero
Shown above are the different impact elevations in reference to the point of aim. The grey dot in the middle is where the sights are set, and the color-coordinated dots are the elevation at which they’d hit in reference to the distance shot. Windage was adjusted for the sake of readability. The rounds aren’t impacting to the left or right, I just didn’t want to stack them all vertically so they could be read easier.
This 25 yard zero is perhaps the most popular for an AR. As we can see, the 25yard and 300 yard impacts are both directly on or near the point of aim. Everything in between seems to hit high, with a drop off afterwards.
50 Yard Zero
With the 50 yard zero we see that the high impacts are almost completely eliminated in comparison to the 25 yard. However, our drop off past 250 yards become much more pronounced. At 600 yards we’ve completely fallen short of even hitting the target.
This zero is popular with a lot of firearms instructors. Ronin Tactics, Speaks about the 50 yards zero in his video on setting up a carbine. Skip to the 13:00 minute mark for the related info.
100 Yard Zero
The 100 yard zero is most popular among hunters, and as a result sees some use in the AR community that come from a more DNR informed background. As we can see, there are no tall shots at all. The point of aim is the tallest the round will every impact, and everything from there is a drop calculation.
There are two other zeros gaining popularity in two very different communities. One of them being practical combat use, and the other being competition.
36 Yard Zero
The 36 yard zero has been gaining traction in military circles. The Marine Corps has been using this zero for over a decade at this point. Shawn Ryan of Vigilance Elite, a former SEAL and CIA Operator, is proliferating this method in his training and media. He even offers a compensated target on his website that allows you to get a 36 yard zero on a 25 yard range.
Honorable Mention: The 200 yard zero has gained traction in the distance shooting community. They never shoot under this distance and often find calculations past this distance easier. I didn’t create an image for it as most of the shots would be all over, and it’s intended purpose just doesn’t make it a candidate for my defensive carbine.
The raw data doesn’t tell me a whole lot on its own. Though, before we jump into analysis, we have to determine which data is even going to be useful for us. For me, my rifle will rarely-if-ever be used past 200 yards. This is important. It allows me to ignore extraneous number sets. While some of you may care greatly about the differences in 600 yard drop distances, I’m not. So, I will compare the following.
Hold at 200 yards
- 25 yard zero: +3.5″
- 36 yard zero: +0.2″
- 50 yard zero: -1.6″
- 100 yard zero: -2.6″
Hold at 25 yards
- 25 yard zero: +/- 0″
- 36 yard zero: -0.4″
- 50 yard zero: -0.6″
- 100 yard zero: -1.8″
Maximum spread between 25-200 yards
- 25 yard zero: 3.8″
- 36 yard zero: 1.8″
- 50 yard zero: 2.1″
- 100 yard zero: 2.6″
Well, the winner is obvious. The 36 yard zero has the smallest deviation from my point of aim at maximum and minimum measured ranges. It also has the smallest variation from my point of aim throughout my intended engagement range. Ignoring most anything past 200 yards allows me to focus on my elevation differences in a tighter area of results.
Anywhere within my measured and considered engagement range my round will land within 2″ up or down of where I aimed. My rifle is just under 2 MOA in terms of mechanical accuracy, so I can practically assume that just under 4″ is the furthest up or down from where I aimed that my round can land between 25-200 yards. That’s assuming I don’t compensate for elevation by adjusting my point of aim.
From aiming at the sternum, that means there is at worst a 4″ x 8″ strip stretching from the base of the neck to the nipple line that my rounds can land (provided my aim is true). On an X-ray machine that area of deviation would show you the spinal cord, heart, pulmonary arteries, ascending and descending aortas, and the inferior vena cava. If you don’t know what all those body parts are, just know they all mean bad times for bad guys if struck. A couple of them are light-switch flips in terms of stopping attackers, the rest are 2 minute countdowns at the longest.
So Why the 25m Zero?
The 25m zero is still a useful standard. While it may not be the best for my particular setup it still holds a lot of value for the infantryman. Shots up to and past 300 meters are a reality of operating environments like Afghanistan.
The hold-overs past 300 yards on a 25 meter zero are much easier to account for than other comparable zero distances. For the Soldier that needs a do-all tool for everything from clearing a room to laying down effective cover fire across a valley, the shorter zero serves them the best for as many situations as any zero can.
The rise between 25 yards and 300 yards can also be a positive in a combat rifle. When the blood is pumping the natural reaction is to want to see as much of your target as possible, which can lead to a natural drop in aim with things like iron sights and obstructive red dots. That nearly 4″ rise at 100 yards can be the difference between a gut shot and a lung shot.
Another possible advantage is shooting a target with partial cover. Rather than try and cover an already hard-to-see target with your sights, you can use your Battle Sight Zero knowledge and aim at the top of the cover. Then let the natural point of impact rise from your zero do the rest of the work in actually landing on your target.
There is a lot more theory to zeroing a rifle for a fight than many think. The perfect zero can change depending on your ammo choice, barrel length, or intended engagement ranges.
I’d encourage anyone doing a serious build to define their intended ranges and crunch the numbers. It may lead to your own small zeroing epiphany.