Thinking Man's Corner

Article by: William G.

This article will focus on the 5.56x45mm NATO cartridge that is still the predominate round of CONUS LE. If you use a 6.8, 300 Black Out, a 7.62x39mm, a 30-30, or a 7.62x51mm NATO, I am not the one to talk to about zero’s for those (except the 7.62×51, but I don’t want to muddy the waters here, so we will keep it simpleish).

Commonly in use twist rates are 1-in-7 and 1-in-9. Sometimes you will find 1-in-8, and 1-in-12 still has a presence with all the DRMO guns floating around agencies. Sometimes, you may even encounter a 1-in-14 on a Ruger Mini-14. Barrel lengths run from 5.5″ on a SIG MCX all the way up to 20″ on the older M16’s. More commonly, we see 11.5″ and 16″ on police carbines.

Duty ammo is all over the place as well. Somewhere between 55-77 grains is usually what we see. The rule of thumb is that the lower the second number of the twist rate, the heavier the bullet you can use is. 1-in-7 will perform best with a 75-77 grain bullet, 1-in-9 will perform with up to a 64 grain bullet, and 1-in-12 is best suited for 55 grain bullets. You can shoot bullets lighter than what I listed, but you don’t want to shoot heavier ones due to destabilization and a number of other performance, accuracy, and safety reasons.

As to the whole thing about 223 vs 5.56x45mm, 223 is a commercial cartridge, and 5.56 is a military cartridge. 223’s normally have a tighter chamber for more accuracy. 5.56 usually has more pressure and velocity than the same grain bullet in a 223 caliber. 5.56 also usually has case hardening and is crimped tigheter, and uses different powders that are more reliable and more flash retardant – with accuracy as a secondary concern to reliability. What does this mean? You can easily shoot 223 in a 5.56 chamber, and the brass will not expand too much to get stuck, and the gun will function normally, unless the buffer or spring is to heavy. However, if you use a true mil-spec 5.56 in a 223 commercial chamber, the pressure may cause the case to expand to the point you have extraction issues. Yes, that is a real thing. Yes, manufacturer’s still mismark barrels. Yes, there is something called a 223 Wylde chamber. No, I do not care about any of that when it relates to LE duty grade guns. I am primarily concerned with Colt, LWRC, Sig, Daniel Defense, Smith and Wesson, HK, and other quality-established Law Enforcement Specific lines.

Ok, so now all that is out of the way, what about zero? the AR style rifle has a height over bore of right at 2.5 inches, meaning the iron sights, or the optic sits 2.5″ higher then where the bullet exits the barrel. There is a reason Mr. Stoner designed it this way, along with a lot of other features on that system that are too much for this article.

When you go to zero the gun, you will get the most benefit from prone, literally proned out on the ground and not at a bench. The target should be as low to the ground as possible, where you are not raising the gun up to it, but rather the target is in line with the muzzle. I do not like bi-pods on an AR, but if you do, that is fine. I also do not like using rests or sandbags. I get the most stability and realism from using the magazine as a monopod. If your gun, magazine, and ammo are all in spec, this will not cause any malfunctions regardless of what your neighbor that was in ROTC during Falklands conflict told you. You do not need any special dingus to attach to the bottom of the magazine either. If it causes malfunctions, something is out of whack.

My recommendation is that you zero the iron sights first, and that you work windage and get it to where it is centered. Then you can work elevation after that. Avoid making windage and elevation adjustments at the same time. If you would like to be extra precise, set your irons to mechanical zero, and then record how many clicks it takes to achieve you desired zero. You can write the finished product on an index card and tape it to your stock, or leave it in a laminated card in your shooting bag for reference.

Now once you have the irons zeroed, you can move on to your optic. Same things apply as with the irons. Make sure to adjust for windage then elevation.

As far as distance for zero goes there are 3 main ones we can fall back on:

100 yards – this is popular with law enforcement because 100 yards is the max distance of a lot of ranges.

50/200 – this is 50 yards/200 METERS and at one time was known as the SOCOM zero. It is advantageous as one can hold the dot in the center of the largest part of the target and hit no lower than 2.5″ beneath the sights, or no more than 2.5″ above the sights – from muzzle contact out to 200 meters. It takes a lot of guesswork out of the equation.

36/300 yard – This is more commonly known as the USMC zero. It actually offers more precision with less deviation than any of the others.

So, which one do I recommend? I cannot recommend a specific without knowing a lot more info. Once you change the length, twist rate, bullet weight and manufacture, as well as, specific load data, you will get different results. So, if you are shooting a 77gr OTM out of a 1-in-7 twist 10.3″ barrel, your results will be different from a 64gr SP our of a 1-in-9 twist 16″ barrel, even at those same distances.

I personally use the 50/200 for the 5.56x45mm regardless of twist rate, bullet, etc. I prefer the 36/300, but the range I have the most access to goes out to 200 yards. I want to be able to confirm my furthest zero. Which leads us into:

Regardless of which zero you go for, start at 25 yards. Use something like the SQT-A1, IPSC, or FBI Q target, and put a 1″ paster, dead center. Get the bullet close to that. Shoot in 3-5 round groups. 3 if you are short on ammo, 5 if you have time and want to get the most precise. Once you have done that, you will be much closer to the further distances. Now if you chose the 36/300, move to 36 yards, and get the bullets touching or in a super tight cluster on the paster. Then you can move to 300 yards to confirm. Same goes if you choose the 50/200. Get them on at 50 yards then confirm at 200 meters. Regardless of your final zero, start at 25 yards.

Jeff Cooper used to use a hill with dirt clods or rocks to get the gun close to zero before moving on to farther ranges. This is just a more refined version of that. You will save yourself a lot of frustration by getting on paper at closer ranges first.

Once you have gotten consistent groups very close to your spot, do not endlessly chase the zero. All the bullets do not have to be touching. Most of the service grade guns, and ammo are not going to shoot into a 1″ group, regardless of what a manufacturer claims. Get as close as you can. Then check it again.

Everytime you go to the range, confirm your zero. Zero’s can change due to humidity, temperature, elevation, the gun being bounced around in the vehicle, dropping it, and all sorts of things. If nothing else, confirm your zero at the beginning of each season. Yes, even if you only use iron sights.

Make sure you put witness marks on the mounting platform of your optic, and the screws on the iron sights. Check them. If they are out of alignment, re-apply the glue, re-apply the marks, and confirm your zero. Zero with the ammo you are actually going to carry for duty, and not cheap range ammo. It doesn’t matter if a manufacturer claims their practice ammo is designed to the same spec as their duty ammo. It is not. It cannot be, or it would cost the same. It may be really close, but close only counts with horseshoes, hand grenades, atomic bombs and presidential elections. Your 22 caliber super magnum +p+ is none of those, so don’t chance it.

There are some other ways to zero such as at 10 yards, get your bullets to hit 1.9″ below the aiming point, and you are supposedly going to be dead on at 100 yards. That works for some people, but has never for me. There are also special zero targets that help. Of them all, I like the Vigilance Elite target, but it is based off the 36/300, even though the initial zero is at 25 yards. I have used it when I had regular access to a 300 yard range, and it worked best of all I have tried. Just google AR zero target (and your preferred distance) and you will get something that works well enough for a rough zero, but please-please-please confirm, through live fire, at the furthest distance.

Whether you follow the above recommendations, or a different protocol altogether, don’t rush it. Make sure you have enough time set to the side when you go to the range to zero. It is easy to rush things, and get frustrated. Use the time to work on trigger control, and breathing techniques, and give yourself a nice break from the rest of the world’s problems.