Over the years, I've come to find that Point Blank Range (PBR) zero is probably one of the least understood methods for shooters of all skill levels. The practical application of using a max PBR is relatively simple, however; there are a few principles and considerations we need to be aware of to maximize its potential. But before I highlight the aspects of practical employment, I'll set the foundations for understanding.
So what is Max PBR?
Max Point Blank Range is the maximum distance a bullet can remain within a predetermined target area. It is measured from the muzzle to the range the bullet drops below the target area. There are a few key aspects to a Max PBR trajectory:
- The bullet will start below the line of sight (LOS), the same amount as your bore height / sight height.
- The bullet will have a near zero and a far zero point along the trajectory.
- The far zero point is usually termed the PBR zero, or battlefield zero.
- The range at which the bullet drops below the target area makes up the max PBR.
- Max range will vary with the target size, bullet type, muzzle velocity, sight height, and atmospheric air density (negligible in most scenarios).
In this instance, I've calculated the max PBR for the following scenario:
Bullet: Berger Tactical 175 Grain OTM
Muzzle Velocity: 2750fps
Sight Height: 2.5in
Temperature: 59F
Station Pressure: 29.92inHg
Relative Humidity: 0%
Density Altitude: 4ft
Total target area: 12in
Target dimension: 6.00in positive and 6.00 negative from center
Let's dissect this image a little bit further, because I usually start to lose shooters at this point:
- This particular weapon system has a sight height of 2.5 inches, so the bullet begins it's trajectory 2.5 inches below shooter LOS.
- The bullet intersects the LOS with a near zero range of 27m.
- The bullet reaches a culminating height (max ordinate) of 5.96in above LOS at a range of 162m.
- Again, the bullet intersects the LOS with a far zero range of 289m.
- The far zero intersect gives the shooter a battlefield zero of 289m where point of aim (POA) is point of impact (POI).
- After 289m the bullet continues to drop below the LOS.
- The bullet falls below the predetermined -6.00in target area after 339m.
- The maximum engagement range for a 12in target in this scenario is 339m before the shooter would miss low.
Practical Employment of the Battlefield Zero
The above scenario means that I could dial or hold 1.2 MIL on any target from 0-339m and hit within a maximum of 6 inches above or below my POA. Note that this weapon was initially zeroed at 100m and the 1.2 MIL adjustment achieves the 289m battlefield zero.
Hopefully you're still with me because now we've laid the ground work, we can address the employment practicalities and errors of a battlefield zero.
Employment of a battlefield zero isn't just reserved for our warfighters on a two-way range, it's also an extremely useful tool for hunting or any other scenario involving rapid engagement of targets at closer ranges. There's a few things shooters need to be aware of for maximum effective employment of a PBR zero.
First and foremost, the most common error I identify when shooters calculate a PBR zero is the use of overall target dimensions; Why not use the largest available target area to increase the max PBR distance? This would make sense, but it doesn't give the shooter any error margin for shot placement on the target. At max ordinate range, shots may fly over the target. At max range, shots may fall below the target. Put another way, some shots may miss if the shooter calculates the PBR for the very top and bottom edges of a target area. Consider the applications of a PBR, it's usually used for rapid engagement of multiple targets. So it's probable the shooter doesn't have time to practice perfect shooting fundamentals. The shooter is more concerned with quickly putting a hit on the target and switching to the next. The shooter might be capable of grouping 0.5MOA all day under low stress conditions, but now the shooter might only be capable of 1 MOA from prone. Add a tripod shooting position to that scenario, maybe the shooter is only capable of 2 MOA. That could turn into 3 or 4 MOA on a two-way range. It's always a good idea to give yourself an error bracket from the target edge if the engagement is moderate to high stress.
Another factor might be the vital zone of a target. Consider a max PBR for a man size target height of 30in. That's a significant target area, but what if the shooter is only interested in shots that will immediately incapacitate or neutralize the threat. That reduces the target height to about 12in, or 6in above and below POA. In this scenario, the shooter has a much larger target area but only a hit within the 12in vital zone will get the job done.
The other most common error I observe is shooters engaging a target with a POA which is not aimed vertically central. Shooters tend to aim for the upper chest area when engaging humanoid targets. That's where the vitals are centrally located so naturally it makes sense. But the correct method of employment would be to align POA on the very center of the target to ensure the portion of trajectory above the LOS remains within the top edge of the target area. In this instance, the shooter would do better to aim near the lower sternum.
An easy to avoid error is over measuring a standard target height. This is another common mistake that leads to calculating an incorrect PBR. The result is observed later as missed shots over the target at close range when the target height is actually smaller than the dimension used for PBR calc. That's a problem which is easy to avoid.
Conclusion
What I've highlight are some of the general employment aspects and practicalities of the battlefield zero. The battlefield zero isn't just reserved for snipers, it's also highly applicable for hunters, PRS competitors, and gas gun work. A more advanced method of PBR application is to start favoring a slightly high POA on longer range targets beyond the max PBR. This would account for the additional gravity drop and drag, further extending the effective employment range of the battlefield zero without having to further adjust your elevation for rapid engagements.
When using a PBR on a precision rifle, I recommend a short range 100 yard or meter baseline zero and adjusting for PBR from there. This will minimize any shift to the baseline zero due to changes in atmospheric air density. The "why" behind this is beyond the scope of this post, but maybe I'll write about precision weapon setup in another post. Using a short range zero isn't as necessary for hunting and other shorter range applications outside of precision LR. In that instance, the shooter might set and leave the weapon zero for a predetermined PBR and target area.
Using a PBR zero is extremely effective under the right circumstances. It is eerily fast when practiced and employed correctly, but the shooter needs to understand the limitations and when a PBR may not be best suited to an engagement scenario.
I've broadly outlined how to manually calc a PBR below, for those that want to know.
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Calculating Max PBR
There's a few different ways to go about calculating a battlefield zero. The different methods usually depend on the features of the ballistic solver. Some devices and apps have a built-in PBR calculator, allowing the user to enter a few inputs and the solver spits out the max PBR. Others don't have a PBR calculator and so the onus is on the shooter. You can achieve a manual PBR calc by following a few general steps:
- Confirm the gun profile and environmental inputs are correct for the weapon system and current air density.
- Set the firing solution output to inches or centimeters.
- Set the target range and weapon zero range for the same distance - 300m is generally a good place to start for a 12in target.
- Populate out a range card to determine the bullet position above and below the LOS.
- Use the range card to confirm the trajectory does not go outside the target area at the max ordinate.
- Determine max point blank range the bullet falls below the target area after the far zero range.
Unfortunately this method is somewhat cumbersome when compared to the ease of a PBR calculator feature, but it will still get you to the finish line. The target and far zero range will need continued adjustment before the shooter identifies the correct distance for a max ordinate remaining inside the target area. That's the hard part. Once the battlefield zero range has been identified, the shooter need only scroll to the distance on the range card where the bullet falls below the negative target area.
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