Weapon Zeroes: Reasons and Seasons

The weather has changed. Tis’ the season for a trigger squeezing.

 

Weapon Zeroes: Reasons and Seasons

The following is a list of some different types of zeroes I have learned over the years. This is a basic introduction to get the gears turning in the minds of our less experienced shooters. I know the learning curve can be steep in regards to firearms, especially in the commercial market. In the military, you don’t have to worry about dozens of different barrels, designs, calibers, and ammo types. Even the height over bore axis relative to the sight axis can change your zero’s and POI at farther distances when using a mix of citizen and military optics and weapons.

These are some considerations for the new shooters to think about.

I, personally, have different rifles for different seasons for different reasons. One should always consider putting a different zero on a weapon or two. Especially if you have a special mission role to fill; Like high angle shooting, long range, short range, or high volume of fire.

For most purposes, a 25 meter/yard zero works great. The 100 meter/yard zero is also very useful.

Most of my guns are zeroed at exactly 25m/y or 100m/y. A few are zeroed at max range. Like the lever guns and cheaper surplus guns. This habit occurred during testing for accuracy with these weapons and learning the max effective range. So I simply maintained the same zero.

The Staff at AP recommends you ALWAYS confirm zero at the farthest distance possible and take notes. These notes are called DOPE. Data On Previous Engagement. This provides peace of mind that your weapons optic is mounted square, plumb, and level. Assuring an effective weapon at point target and area target ranges.

 

The Zeros

General Purpose: Weapon is zeroed with any sort of preferred ammo at the distance you are most likely to use the weapon. Such as, your favorite hunting rifle zeroed with your favorite hunting ammo, at the most likely distance you will take an animal. You don’t plan to use the rifle for any other role except to take game, or a potential predator of the two or four leg variety. This can also be used with a cheaper brand of ammo you have selected to break in a rifle before you zero for your preferred bulk and premium ammo. Later, after cleaning your barrel properly and inspecting the weapon for wear and tear, you can sight it in correctly using one of the other zeros listed below.

Co-Witness Zero: Zero your optic and your iron sights separately. They should be close, if not the same, when co-witnessed on the same range settings. Later, after you zero; You can use either the optical zero, or the iron sight zero, to confirm that your weapon’s zero hasn’t shifted do to hard use. Like “hard and heavy” vehicle operations or airborne operations where there is a high chance of impact on your weapon’s optic.. If you drop your weapon, for whatever reason, you can use a co-witness zero to provide peace of mind; confirming if one, the other, or both are still on target. On occasion, if you run a lot of obstacle missions, you don’t have to worry about banging your weapon around on walls, ladders, rocks, or logs during your course of navigation over, through, or around the obstacles.

Combat: Weapon is zeroed without taking the ambient temperature or barrel temperature too seriously. Knowing during an extended engagement this will likely change due to the reasons listed below. You may also receive a resupply of ammo that requires you to confirm zero, but not have the time or space. You should consider preparing to make your adjustments to your optic if necessary. This a general purpose zero for combat operations, patrolling, and general purpose kinetic operations. This works well when you are shooting from heated or air conditioned vehicle, but may dismount into an environment that is a different temperature from your vehicle or building. This is important to consider during urban operations. You can skip the heat and A/C to prevent any possible problems.

Clean/Cold Bore: Weapon is zeroed firing a very low round count, with a long pause between each round fired, and maintaining a barrel at ambient temperatures. Barrel should be kept “cool” and the bore should be kept clean. This is a good zero for a “Shoot and Scoot” Guerrilla. Fire a few rounds(5-10) and then run. You must maintain the same standard for consistency; Clean bores for cold bore zeros. Inspect rounds prior to firing for case defects or bullet deflects.

Hot Bore: Weapon is zeroed when the barrel is “hot”. This is a good zero for getting into high round count engagements. If your barrel has a thermal shift, you are going to want to use this zero because a barrel with a thermal shift usually has this phenomenon occur after a magazine, or two, is fired. Groups typically open up to double the size of cold bore, and the thermal shift can be quite significant. This requires testing. Let the barrel cool after testing, clean the bore, and then fire a 10 round group(slowly) on a 25 meter zero target to observe the offset of the cold bore zero after you adjust for your thermal shift. Save this zero target for your reference. Record the data for the weapon, ammo type, round count, and ambient temperature/humidity. This is the most expensive zero, not all shooting ranges allow these kinds of round counts. Some powders get heated in the camber, and this adjusts the burn rate of the powder. Which changes zero.

Varmint/Predator Zero: Zero your weapon for the exact distance you will be taking a shot to defend your chickens, goats, or other beloved creatures. Typically from the door to the coop. Or from the porch to the wood line.

High Angle Zero: If you live in the mountains you may have noticed that your flat land zero is not the same as your high angle shooting. Research this, because the topic is quite exhaustive. High angle shooting from a mountain is, mostly, the same as high angle shooting in an urban environment.

Winter Zero: Weapon is zeroed precisely during the peak of the cold season. Your weapon should be the ambient temperature. Allow weapon time to acclimate when removed from a building or vehicle..

Summer Zero: Weapon is zeroed precisely in the sun, on a hot day. Your weapon should be ambient temperature when zeroed. Be sure that both sides of your weapon receive sunlight, or better yet, stand your weapon up on a bipod or rest just like you would be shooting.

Spring Zero: Weapon is zeroed during spring, in the shade, because there will be leaves on the trees. Check to see if the “sun shift” affects your zero.

Fall Zero: Weapon is zeroed in the fall season, in the sun. There are no leaves on the trees, so you should expect your weapon to be in the sun. Check zero from a shaded position once your weapon has cooled down and you have cleaned the bore.

-Some considerations-

-A day zero at 70 degrees may be different than your nighttime zero in 40 degrees.

-If you borrow a magazine from a teammate during an extended engagement, your lot/brand of ammo may vary from your teammate’s lot of ammo. And vis versa.

-Hunting ammo is not the same as match grade ammo. Although it can be quite accurate and appears to be match grade, or near match grade. You may have the odd “Flyer” due to manufacturing flaws for a variety of reasons.

-Your zero may be significantly different when using a different type of ammo, such as 55 grain vs. 62 grain 5.56. This is also true for 7.62’s, 6.5 Creedmore, .300 WinMag, and 8mm. Don’t assume the different grain types and brands are interchangeable, even the various AK rounds.

-Take down weapons, depending on the design, rarely return to zero. This includes removing and remounting optics, despite the claims by even the most prominent manufacturers. Typically they are VERY close and predictable.

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About the Author: Johnny Paratrooper

Born and Raised in Baltimore City, Maryland. History Degree. 8 Years Airborne Infantry and Scouts Platoon. Iraq Veteran. 4-5 Years as a doorman, bar back, and bouncer in Baltimore. Worked in Construction, Heavy Equipment Demolition, Corporate Security, Sales, Forest Service contractor, and the Hospitality Industry. Raised Catholic. Hobbies are race cars and sport bikes. Side projects are HAM radio credentials and long range shooting. MY EMAIL IS [email protected]. Founder of Green Dragon Academy https://www.patreon.com/GreenDragonAcademy

14 Comments

  1. James February 20, 2021 at 13:14

    Thanks again Johnny. Seems zeroed in is your focus of the week or two.
    A lot of variables given ammo/temps ect, so breaking out oddity rifles in different seasons a good idea.
    I will say me removable PEPR mount,Burris along with a mark on rail to reorient so far has worked very well holding in zero,purposefully remove and install many times to check,have on a few and the aimpoint seems a always steady holder remounted to original zero on rail.
    I personally have never noticed much difference in zero excepting really hot weather (90+),that really does seem to throw things around a bit.
    I have luckily a new place/property to shoot on out to 300 yards or so and thus can practice more and have more chance to find/deal with seasonal changes and try me hand regularly beyond the 100 yard mark.

    • Johnny Paratrooper February 20, 2021 at 13:32

      No problem. I wanted to lay down a good foundation for weapon’s zeroing before I dove into some more serious topics. I am glad to hear that your optics can be remounted and maintain zero. The ability to remount an optic appears, in my experience, to depend on the mating of the two. Some optics are more forgiving than others, most likely do to the choice of mounting solutions. I know that several of my weapons do not like having their optics removed. They always seem to need a few clicks afterwards. However, I don’t needlessly remove my optics anymore. It just creates more work, and frankly, it’s not easy for me to zero.

      • James February 20, 2021 at 17:06

        Sigh….,forgot to mention I really locktite and torque mounting to mount screws for scopes/dots ect.I will say with just them torqued but not lock tited was amazing how quick they could move,cross hairs at angles after a few shots ect.,bless blue locktite.
        I have enuff to work on with all this,am not ready for your more “serious” articles(will read and heed anyhow).
        I only get zero or as close as I can thru a lot of table/bag/friend spotting help(and this is just 100 yards!).
        I wonder if the high temps are tweaking me mounts or what it is about them that affects shots for me,perhaps the high temps just throwing me off.

        • StormN February 21, 2021 at 14:56

          Thanks for the blue locktite idea. Will have to try. I live in Arizona. I do know from experience direct sunlight affects sights (not just temperature) – it heats scope up. I have a camoflaged piece of cloth loosely velcroed over my scope – keeps direct sunlight off. I have not yet tested this for results.

  2. weasel74 February 20, 2021 at 18:18

    For you snipers out there, cold zero is a pain in the ass but very important. Depending on your barrel, you could have as much as a 3 inch difference between your cold shot ( first round of the day out of a cold barrel) and one from a hot barrel at 100 yards…and this from dedicated, bolt action sniper rifles. Some guns will be this way, some won’t, even from the same manufacturers. You have to know YOUR gun obviously.
    Imagine, you’ve stalked into position, waited for your shot, target presents itself and you press off your shot at three or four hundred yards with your cold barrel. If you are going for a head shot and relying on your zero that you’ve confirmed with a hot gun a dozen times, you’re going to miss. That’s if you have a rifle with significant “thermal creep” as JP puts it.
    If you’re doing sniper competitions running a hot gun all day, a hot zero is better but point being, you need to be very aware of this.
    From experience, active sniper for thirteen years, tens of thousands of cold shots and have burned through a couple dozen sniper rifles at least…
    Happy trails
    Weasel

    • James February 20, 2021 at 19:57

      Weasel,how does one zero a cold barrel if first shot a miss?Say my neck of the woods actual temp goes 10-20 degrees on average coldest,if first shot a miss for zero how long to wait till trying again?I assume(?)wind chill factor beyond wind not a factor excepting me if not properly dressed out.

      • weasel74 February 21, 2021 at 00:25

        Hey James,
        Wait 30, 40 minutes until your barrel is at its natural temp, adjust your dope and do it again till it goes where you want. Again, some barrels will have a dramatic difference, others will have none. Be well.

        • James February 21, 2021 at 10:16

          Thanks Weasel,enjoy the weekend.

  3. Matt Bracken February 20, 2021 at 19:59

    Thanks again, Johnny P, for “keeping it real” and giving us a lot of “real world” variables in our mental equations.

    • Johnny Paratrooper February 21, 2021 at 09:50

      Thanks! I know I have had some troubles in my day zeroing a few rifles. I have a Mosin-Nagant that shifts 2 inches at 25 meters after 5 rounds. Which is considerable and ridiculous…

  4. HMFIC May 6, 2021 at 09:10

    I’ve struggled zeroing some weapons over the years. I think it is more my fundamentals of marksmanship versus the quality of the firearm or ammo. Would love to see some info on that as well. Thanks for the post!!

    • Johnny Paratrooper May 6, 2021 at 09:43

      I’ll put this on the list. There are several variables that can effect zero.

    • boss21 November 16, 2021 at 20:00

      Good stuff. This is why I cringe when I see guys with oddball calibers and custom rigs twisting knobs while we are ringing steel.

      Standardization hewing close to .mil is key. 5.56 , 7.62 /39,7.62 NATO and 300 Win Mag is all I need. Perfect? No, but I know where they hit . I have other toys but that’s all they are. Reloading is a given.

  5. Anonymous July 14, 2021 at 07:08

    3

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