The Fallacy of “Combat BZO”

I don’t know who came up with this, or why so many officers and NCOs seem to think it’s gospel, but this is a concept that has to go away.

The idea of the “combat BZO,” and I’ll get into BZO (battle-sight zero) in a minute, is that in order to have your weapon properly zeroed for combat, you have to zero it while wearing all your kit, because somehow the kit on your chest and head changes the impact of the round.

Anyone with the slightest grasp of basic mechanics should see in a matter of moments how wrong this is.  The zero is a mechanical relationship between the alignment of the sights and the barrel.  Nothing more, nothing less.  If your weapon is properly zeroed, then correct sight alignment, sight picture, breathing, and trigger control will cause the round to impact where it is aimed.  That is all.  If you are off because you’re wearing your kit, it has nothing to do with your gear, it just means that your gear isn’t set up correctly for you to get proper sight alignment, in which case you need to fix your kit.  The whole concept of “battle-sight zero” being somehow different from a strict zero is equally flawed.  A zero is a zero.  Either the sights are properly calibrated to the track of the bullet, or they aren’t.

The only thing trying to zero in armor, ammo, water, and helmet ultimately does, is create enough discomfort that it becomes more difficult to group well enough for a solid zero.  The end result often turns out to be a “good enough” zero, which might be in the ballpark, but isn’t really on.

Unfortunately, what should take only a few moments of thought and common sense seems to elude a lot of people, and often those with the rank and experience that they should know better.  I’m not sure where it comes from, though I suspect it has something to do with following procedures rather than really getting to know your tools.

A carpenter knows his tools.  An electrician knows his tools.  A shooter should know his tools at least as well, certainly understanding how they function at a level higher than “pull the trigger and it goes bang.”  Simple, easy-to-acquire knowledge, not to mention a handful of seconds to think, would make this disappear, and get back a lot of wasted time and ammunition.


21 thoughts on “The Fallacy of “Combat BZO”

  1. Canadian

    I disagree- sort of. Yes a zero is about the sight and the weapon system. And if you are shooting bench rest then that is all there is to it. If you actually take large groups into account however (think 20 rds instead of 5) then your MPI might shift because of the way you cant/hold the weapon etc. Many soldiers don’t ever shoot a group larger than 5 rounds, but your average MPI can easily differ if you do. Also, a combat zero shouldn’t really change the elevation, but where your windage is zeroed (assuming there is no wind on zeroing day) can change based on your position and hold. My point being that small groups and aligning the weapon slowly are great on a conventional range- but when the time comes to really pull the trigger, your kit, and the position you take due to your own fatigue will effect where the round strikes. You don’t just zero the optics to the weapon, you zero the optics to the weapon and how YOU fire it.

  2. You just made my point. The zero isn’t changing–fatigue is making the shooter sloppy. That’s why you train stress drills. As a sniper, we did a drill where before you shot the next string, you had to sprint between yard lines, then do 15 burpees before sprinting to the gun and shooting the course of fire. We didn’t get to adjust the windage to accommodate how we were handling the weapon while fatigued; we adjusted for wind and range and took the shot. Same thing with square bay. Believe me, after eight hours on the square bay in full kit, you’re plenty fatigued, but you’ve still got to shoot the course of fire. If you’re point of impact is shifting due to fatigue, whether you got a good solid zero in the prone or a shaky one in gear isn’t a factor. The fundamentals don’t change. The key to fixing that shift is training, not a sloppy zero.

    1. Canadian

      I agree in principle, but I have SEEN soldiers shoot differently with gear on then without. Not just from fatigue. For example, shooting prone with kit on is different then without. I’m not saying that most of this cannot be eliminated through training- the weapons test that I am required to do involves a run down starting at 400m and different applications at each 100m point from different positions. However, as a sniper you will know that no one thing can eliminate all issues, but multitudes of small changes turn a near miss into a solid strike in the t-slot. Giving soldiers free floating barrels doesn’t change their precision over night, but adjustable butt stocks, interchangeable pistol grips, free floating barrels, accu-wedges- and TRAINING all work to incrementally make groups shrink.

      The main issue that I have, is WHY NOT fire EVERY application in full kit? What is the issue? Yes in an ideal world the soldier is just like a bench rest vice, but most soldiers don’t have the option to wear the most perfect gear for their body shape, and as such their gear can change the way they fire a rifle. If this wasn’t correct, then the first day you join the Army (police SWAT etc.) you would figure out where your optics have to be for correct eye relief, and forever thereafter an armourer could bench rest vice zero every soldier’s rifle. In practice this would not actually work, at least that is my experience.

  3. I’m sure you have seen soldiers shoot differently in kit, but it has nothing to do with the zero. That’s a case of the kit throwing off sight alignment. If your kit is interfering with your shooting, you need to adjust your kit. Trust me, I’m a lefty, and had to adjust to shooting with the fast-tech on my helmet strap interfering with my cheek weld. But a zero is a zero, and my argument against zeroing in kit (note, I’m not against the rest of the training being in kit) is that you should have the best zero you can get, and the instability of shooting in the prone in gear works against that.

    I have zeroed slick, then reconfirmed with gear. If your fundamentals are correct, there is no impact shift.

    1. Getting a zero on your rifle is simply aligning your line of sight with your line of bore at a given distance. There really isn’t anything more to it than that. There is no reason to zero in full kit, or in a stressful environment, that just contributes to setting a bad zero from the get go. Training as you fight, in full kit, now that I completely agree with. As Peter points out, the reason why soldier’s shoot differently while wearing full kit is because their body armor, helmet, ect… are making it difficult for them to get a proper sight alignment so they are trying to muscle that front sight post into the center of the aperture. Training in full kit to get used to shooting with it on, adjusting it to help get a better sight picture, and generally getting to know how your kit and rifle interacts with each other during live fire exercises is a great idea but I see no reason to zero with kit on. BZO sounds like something a 1st Sergeant misunderstood about setting a battlefield zero which is a completely different thing.

      1. Canadian

        Perhaps we are talking about slightly different things, I am referencing optics not irons. It is approximately the same, but you can’t muscle a front sight post to zero optics- it’s just on or it’s not- that could be the whole difference in our discussion right there.

      2. True, but you can certainly attempt to muscle the reticle onto the target to attempt to compensate for an uncomfortable shooting position or bad stock contact with your plate carrier or other kit.

    2. Canadian

      Right, but there comes a point where you cannot adjust kit anymore- plates are plates and they are always the same size etc. If the kit throws off your sight alignment, then you have made my argument for me- in that you then zero with that “off” alignment- which is now “on” once you have made your adjustments. In the end, once point of aim is point of impact you are on, regardless if you shoot upside down from a scuba tank. The BDC in most optics compensates for 90% of drop, but there are still minor adjustments to be made by the shooter.

      Perhaps we will just disagree.

      1. Yeah, I just don’t see you muscling your way to a good sight picture the same way every time because of the way your weapon is interacting with your kit. It is not going to be consistent the way you can get consistent cheek to stock contact or trigger squeeze. This would also theoretically mean having to re-zero your weapon every time you adjust your kit or risk losing your zero.

      2. Plates do come in different sizes. If your plate is too big, you need to go smaller. And yes, I’ve worked with some guys who were shrimps, but somehow didn’t have enormous plates that meant they couldn’t apply the fundamentals. There is no magic to optics; you still need proper sight alignment with the ACOG, just like with irons. That dark crescent along the side or top of the scope? That’s called scope shadow, and it’s going to throw off the impact of your round just as effectively as having the front sight post on irons off to one side. Shooting is not about having a magic zero that works no matter how jacked up your position is. It is about applying the fundamentals, and those are physics. They don’t change.

  4. Canadian

    Again I realize that the fundamentals work, however as my name states I am a Canadian- and we have one size of plates only. We also often fight the “issued kit only” battle, meaning that at even though I am the most common size in the Army I still can’t reach my far right magazine pouch with my left arm, kit doesn’t fit me.

    I’m not talking about having a jacked up position. As you wrote- scope shadow is an issue- which is corrected with proper eye relief. The position of my optics and lenght of the adjustable but is different when I am wearing armour, and a tactical vest. That’s why I zero a new weapon wearing my kit. Those are the issues I am referencing. Fundamentals are always key, but zeroing with your gear just means you have more realistic groups when comparing your zero to a combat shoot.

    1. I wasn’t aware that Canadians only had one size plate. That sucks. You’re definitely being set up for failure.

      In that case, you’ve got to do what you’ve got to do, but just understand that all you’ve really got is a “ballpark” zero. Pat McNamara, who knows of what he speaks, somewhat addresses the issue here:

      What I wrote still very much applies to US personnel, however, who still have the option to size up or down with their plates.

  5. I have only been shooting for 20 something years, and instructing for roughly a touch over 15 of those years, which means one thing, I have more to learn. With that, I can tell you what I HAVE learned. Shooting is not just putting the bullet in the 10 ring, it’s getting your students to BELIEVE that the shot counts, and that each one made properly will save the life of someone important. How have I tried to accomplish that? By making them wear their KIT, and add stress to the normal qual course. Is it required for the US Navy? No. Is it going to be? Absolutely. So really all I have done (other than make more confident and deadly Sailors), is to get them ready for the more difficult qualifications to come, and HOPEFULLY prepare them to squeeze the trigger against an aggressive target if the time arises. THAT said. Sights are zeroed to the weapon. The only real change is if you place the front sight on top, under, or split the bullseye. If you zero it wearing jeans and a t-shirt, then adjust your stock, KIT placement on your shoulder, whatever you need to do, to make sure that you can use whatever optics (or iron) your weapon has on it. My 2 cents.

  6. steven

    So, I know where this is going to go.. but.. what distance do you zero a rifle at? This “could” be the reason why BZO gets used too much, w/o the NCO understanding the reasons and actual definition behind the original intent of “BZO”.

    1. The 36 yard BZO target used to be the standard. With an M4, the bullet has the same point of impact at 36 yards and 300 yards. You set your sights for 300, and aim at the black at 36. The projectile is still rising at 36, and passes through the same line of sight as 300.

      With the ACOG, this is a little different. The ACOG is set up to be zeroed at 100. With the magnification, there really isn’t any reason you can’t zero it at 100 yards, but if you are having a hard time getting on paper, or have limited space, it is possible to zero at 25 yards. The impacts will be low at 25. Here’s a good example of a 25 yard optics zero target:

    2. I should also add, and this is coming from an actual USMC pub, that BZO is zeroing the rifle at 300, so that you have a good mid-range zero. This means you shouldn’t have to adjust your sights for reasonably accurate shots out to rifleman distances, i.e. 500 yards and in.

      1. Canadian

        That makes decent sense. I have rarely done this with 5.56, but with 7.62 I shoot “reverse image” zero.
        Meaning the rifle is zeroed for 500m point of aim point of impact. Then following the rise and fall of the round between 0-500m, if you aim at the bottom of centre of mass on a man sized target, the round will strike the bottom centre of mass (torso) at 0m and then will rise to the top of the torso, and back down to the point of aim at any distance between 0 and 500m. In this manner (when using optics) there is no requirement to change any settings for a rapid torso hit onto a target.

  7. PFC Carter

    This is 100% correct, I guess some people just don’t pay attention to detail like they used to… It’s simple physics/common sense. I don’t see why the canadian didn’t understand, you laid it out perfectly. I don’t see why anyone wouldn’t see this as a child when they first understand what zeroing is.

  8. Pingback: Fight as you train (American Praetorians) | Breach Bang Clear

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