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Hunting season is upon us, and as I bagged a mule deer on opening day I have plenty of time to write on a topic that has helped me both in combat and while on the hunt.  That topic is called "Maximum Point Blank Range" or MPBR. 

The idea is that instead of zeroing at an arbitrary distance, you zero for a distance that allows your bullet to travel no higher or lower than a specified height from your optical centerline.  Let's break this down.

The most common analogy used to explain MPBR is shooting through an extremely long (and theoretically perfectly straight) tube.  You want to aim down the middle and find the farthest distance where the bullet touches neither the top nor the bottom of the tube.  The diameter of the tube is defined by the height of the kill zone of what you're shooting at.  If I estimate the kill zone of a Sitka Blacktail to be 5" tall, then I want to know the max distance where the bullet travels no further than 2.5" above or below my point of aim, allowing me to hold center on the target and not worry about holdover or adjusting elevation turrets.

Using the above mentioned 5" kill zone, and using the data from my bolt action .308 rifle that's firing a 168gr round with a muzzle velocity of 2648 FPS and a ballistic co-efficient of .447, we get the following numbers.

With a 100 yard zero, the round never travels appreciably above the line of aim, and falls to -2.5" around 185 yards.  So, from point blank to 185 yards I could hold centered on the heart and expect much joy.

With a MPBR set for 5", I'd have a near zero at 24 yards, a far zero of 207 yards and a MPBR of 243 yards.  The round has a peak of +2.5" at around 115 yards.  Using the MPBR method, I could hold center on the vitals from point blank out to 243 yards.

This method is even more effective with rounds that drop faster, as adding a little pre-zero height above aiming point helps stave off significant rate of drop for even longer.  There are a number of online calculators for MPBR, so take a look at one, crunch some numbers and see if this method works for you!

-Rex Nanorum

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