Gun Gear

Maximum Point Blank Range and the Battlesight Zero

The MPBR is the maximum range at which the bullet rise and drop stays within the vital area of your target. Anyone who has been in the U.S. Army or Marine Corps is familiar with a battlesight zero or improved battlesight zero (BZ0 or IBZ0). The concept for an MPBR or battlesight zero is pretty much the same: zero the rifle so that you get a point of aim that is effective over the longest range. The battlesight zero used by Marines when shooting the iron sight M16A2 is the 36/300 zero, meaning that the bullet will be on the sight line at 36 yards and again at 300 yards. The US Army uses what is referred to as an improved battlesight zero, which calibrates the rifle to be dead on at 50 and at 225 yards. The USMC also uses the 50/225 IBZ0 for M16A3 rifles equipped with Trijicon ACOG scopes.

The illustration above demonstrates how a battlesight zero works. The bullet is fired from the barrel and rises up to be exactly on the line of sight at 36 yards. It then continues to rise, topping out at 6″-7″ depending on the round used and the barrel length of the rifle. It then descends until it is again exactly on the line of sight at 300 yards. This gives the Marine a good aiming point for a man sized target at any distance between 0 and just over 300 yards.

From the USMC manual:

If a rifle is zeroed for 300 yards, the bullet crosses the line of sight twice. It first crosses the line of sight on its upward path of trajectory at 36 yards, and again farther down range at 300 yards. Since a bullet crosses the line of sight at 36 yards and again at 300 yards when a rifle is zeroed, a rifle’s zero may be established at a distance of 36 yards and the same zero will be effective at 300 yards. It is critical that a Marine fires tightly grouped shots directly on the point of aim when establishing a BZO at 36 yards because any error in shot placement at 36 yards will magnify as the bullet travels down range. If the rifle is properly zeroed for 300 yards/meters, the trajectory (path of the bullet) will rise approximately 7 1/2 inches above the line of sight at a distance of approximately 175 yards/meters. At other distances, the strike of the bullet will be less than 7 1/2 inches above the point of aim. Only at 36 yards/30 meters and 300 yards/meters does the point of impact coincide with the point of aim. If only a portion of the target is visible (e.g., the head of an enemy soldier), the trajectory of the bullet may have to be taken into consideration when firing at a distance other than 300 yards/meters. If a Marine does not consider trajectory, he may shoot over the top of the target if the target is small and at a distance other than 300 yards/meters.

The 50/225 IBZ0 is useful as the bullet has much less rise at the midpoint of the trajectory. Its shorter effective range is more suited to urban and jungle warfare where visibility is limited and most engagements are at close range. The fact that the bullet rise is lower means that shots taken at ranges between 0 and 250 yards are much more accurate, with a bullet rise less than 2 inches at the midpoint of the trajectory.

The battlesight zero as a concept is very useful to hunters as well. When hunting deer, or any medium sized game, it is rare to know the exact distance that the quarry will be encountered at. Luckily, if your rifle is properly sighted in for its maximum point blank range (MPBR) you don’t need to know the exact distance. While the ballistics vary from rifle to rifle, it is generally a simple matter using any number of online ballistic calculators to work out what the ideal zero for your rifle should be. The most critical calculation is your second zero. Based off of the size of the vital area of your target, you can compute the maximum rise and drop tolerable for your cartridge. Most white tail deer for example have a vital area that is generally 10 inches in diameter. Mule deer, elk, and moose have vital areas that are significantly larger. A large mule deer has a vital area around 12″ in diameter, an average elk around 15″, and a good sized moose nearly 21″. A hit from a medium caliber rifle to this area will result in a quick kill. Therefore, if we are hunting white tailed deer, we can tolerate a maximum rise and drop of 5″. Using this value, it is simple to calculate that the MPBR for a 180 grain Remington Core-Lokt .308 roundnose soft point cartridge in my trusty Remington 700 is 293 yards, with our second zero at 252 yards. With our rifle zeroed for these distances, we can be assured that a perfectly centered aim on a deer at any distance between 0 and nearly 300 yards will result in a hit in the vital area of our target.

The problem with zeroing your rifle for 293 yards in this case is that not many people have access to a 300 yard range. Not to worry, there are other ways to achieve the same zero for your hunting rifle. As it mentions in the USMC manual we referenced above, you can sight in your rifle at a closer range for the same result. In fact, if you have a good bench rest and a gridded target you can, with a little math, perfectly achieve a MPBR zero on your rifle at any range. Lets assume for this example that our range only has a 50 yard rifle range. We’re shooting a Remington 700 chambered in .308 and plan to use the 180 grain Remington Core-Lokt mentioned above. By plugging in the information for that load, we can see that the bullet should hit 2.2″ high at 50 yards (if you were at a 100 yard range, it would hit 4.45″ high). Our first zero for this rifle and cartridge combination is actually just shy of 20 yards, and you can use that distance if that is the only range available at your local shooting gallery, but be aware that minute errors in measurement which may not be apparent at that close range will be magnified at longer distances, possibly throwing your shot off.

Remember: The Battlesight Zero and Improved Battlesight Zero discussed here only work on 5.56 M16 and AR-15 style rifles. You will need to find the maximum point blank range for your unique rifle, optic, and cartridge combination. Even differences such as the scope you have mounted on your particular rifle will change the MPBR and subsequent zero. Find the manufacturers information on your favorite rifle load, google up a ballistics calculator, and in just a few minutes after plugging in your data you’ll have a good MPBR zero for your setup.

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Comments (36)

  1. The Gunnery Sergeant in Full Metal Jacket was a real Marine. Do you think he made up all of those insults on his own or were they a cumulation of excerpts from his growing up in the Corp. I am retired Army SF and my use of swearing was dependent upon target audience and the emphasis I wished to impose…a verbal METT if you will. Now we have a military where Affirmative Action Figures are more cherished than warriors as the Ultimate AAF has converted the military more into a Camouflage Welfare System and Social Experiment than even the Clintons. Of course we would never put these same ridiculous standards on our professional sports teams because winning is everything when it comes to accumulating trophies on an annual basis versus maintaining U.S. economic and military superiority. So without swearing I have agreed with Frank to explain how some people just don’t get the point with politeness because they make their half-assed opinions their religion. For the moron who stated that bullets don’t rise, just put your science to the test by vising in a rifle zeroed at 300 yards on a target 24″ high and the straddle the line of sight at 100 yards. At a minimum he won’t procreate the race anymore and this planet will indeed be a better place.

  2. “What does change is the trajectory of the individual bullet/cartridge.”

    PK,
    What exactly do you think trajectory means? It’s the curve of an object in flight, otherwise known as the RISE and FALL of an object.

  3. This post is to congradulate Nick in post 24 for correctly answering the original discussion from the rude and always right post from paul ( post 10 ) haha. Though i believe he is right when he says that the trajectory will not rise above the angle that it is fired from because of gravity, he will not understand until someone explains that there are two angles to consider. First the angle of the line of sight from which you are aiming via iron sights or scope, and the angle of the barrel itself. for example lets say you start off with a rifle that has its sights perfectly aligned with the barrel and you try to hit a target say at 400m. Most likely you will hit low so what do you do ?… you adjust the rear sights which actually raises the rear sight in elevation. This naturaly makes the shooter bring up the front sights a little to realign the sights. Now the barrel is angled up in reference to the angle of the iron sights/scope. The angle of your sights and or your view when aiming will be 0° in reference to the target because this is what your doing when aligning your iron sights with target; but now your barrel is angled up slightly. Now you may hit your 400m target with the arc of the trajectory allowing for further distance. I have never been in the military, but now am thinking that i should have signed up just to teach some of these hard headed leathernecks a thing or two about the first thing you should learn as a leatherneck…joking. I am sure the Magnus effect is real, but to the discussion of trajectory rise, it is im sure just a small part of the causes of trajectory rise. no need for formulas fellas, just a minor backround in shooting tin cans and jack rabbits ; )

  4. Chiming in on what was stated by Tom in post 17, follow this link for a better explanation http://m14forum.com/m16-ar15/29561-adjusting-your-iron-sights.html If not, in short, we (as in Marines) set our sites for 300 yards. The sites will angle the rifle upwards because of gravity pulling the round down. Even though you feel as if the rifle is level, it in fact is not. So you are slightly angling the rifle up, through trajectory, the round crosses the same elevation at 36 yards and at 300 yards. If you really want to try it out, go sight in at 36 yards. Then go set up some new targets at 36, 150, and 300 yards all in line with their dead center bulls eyes being at the exact same elevation, including the tip of your barrel after being mounted in a vice and aimed for the 36 yard target (now this is for the M16). If you don’t know how to make them all the same elevation, go to home depot or lowes and buy and learn how to use an auto rotary laser level. Before pulling the trigger, get a precision level and see how far your barrel is aiming upwards, thus showing you that the round goes up because you are pointing the rifle up, but aiming your sights level. If this were to be setup precisely with no distractions to the round while carrying the 300 yard length, you would have a hole at the 36 target and 300 target to be fairly fairly close to the exact same elevation while the 150 yard target would be much higher.

    Maybe I’m stating the obvious for some, but I know that what else I was taught in this great gun club I am proud to be a part of, is that sometimes you just have to make it Barney style for some.

  5. Even though this post is old and although some have posted since it’s beginning, I had to say something. First, PK posted on April 30, 2010 that a “bullet NEVER rises once it leaves the muzzle of any firearm.” I can’t tell if he is joking or if he is that damn stupid. It is evident he has never been in any of the Combat Arms MOSs (if he was even in the military). A simple search on the internet under “ballistics” would have ended that noise. Second, Tom rebuked Frank for his foul mouth, which was appropriate. “Political Correctness”? shoot, that’s only common decency. Frank should have learned that at home. I am Old Army, here is a quote for thought: “Swearing and verbal filth is not the mark of a soldier (or Marine?). It is a poor crutch for a man with a small vocabulary and in most cases, little intelligence.” That was a direct quote from Pamphlet 21-13, Department of the Army September 1964). I’d hate to think the USMC would disagree.

  6. brad, the jetboat and car are both curved on one side and (relatively) flat on the other. the same principle you describe states basically that if the air on one side of an object is moving faster than the air on the other side of an object, it will create lift. the bullet trajectory is not affect by this as the projectile is of uniform shape (in theory) so that the air is traveling a close enough speed on all sides to not create lift. at least this is my understanding, its been about 12 years since ive taken a physics course.

  7. a bullet will rise with enough force pushing it foward thats why jet boats or cars going fast enough will fly if going fast enough

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