Maximum point-blank range, MPBR, is definable as the maximum distance you don’t need to hold over to place a shot into a defined target area.
Sounds a bit nebulous, right?
The idea is to zero your rifle to maximize the range you don’t need to hold over but still place shots on target. Granted, the distance and the target area (point of impact) are negotiable, which we’ll go over.
It’s an old method for zeroing a rifle’s optics or sights, but for a general-purpose rifle kept either for hunting or defense, it’s still very viable. For a precision target rifle, probably not so much, which we’ll also get into.
If you’re wondering about how to zero your carbine, be it an AR- or AK-platform rifle in 5.56mm or 7.62x39mm, or even.300 Blackout, it’s definitely worth considering so long as it meets your needs.
Let’s go over what that means in a bit more detail.
Maximum Point Blank Range In Action
Let’s say that a person hypothetically has a rifle chambered in God’s Own Cartridge of .30-06. Let’s also say that the shooter doesn’t want the shot to land in an area any larger than, say, an 8-inch circle, about the size of the vital zone of most game animals.
To find out what that distance is, you use a ballistic calculator to calculate the trajectory. You’ll need to know the muzzle velocity, grain weight, and G1 or G7 ballistic coefficient of the cartridge you use, as well as the height over bore of your optic.
All figures come from the ballistic calculator at Shooter’s Calculator. They also have an MPBR calculator, but its figures don’t always jibe with the trajectory calculations…so be careful!
What you’re looking to find are the parameters that put the point of impact no higher than 4 inches above nor 4 inches below the point of aim. This is done by adjusting the value for the zeroing distance until you find the correct setting.
The figures we’re using is the recipe for 150-gr Remington CoreLokt, hunting ammunition for the Everyman. It has a G1 BC of 0.314 and a typical muzzle velocity of 2800 fps, and we’re using a 1.5-inch height over bore, common for most scoped bolt guns.
Here’s the trajectory table to 500 yards when zeroed at 100 yards:
As you can see, POI is below POA to 100 yards, then starts to drop, falling more than 8 inches by the time the bullet reaches around 240 yards. However, let’s recalculate for 200:
POI is never more than 2 inches above POA but hits 6 inches below POA, a hair past 275 yards, a modest improvement.
But this is about the absolute furthest you can shoot the rifle without having to hold over to drop the bullet within 8 inches of the reticle. How far can we take that out?
Almost 300 yards, as a matter of fact.
With this load, the trajectory with a zero of 252 yards puts POI a hair under 4 inches high at 150 yards and a hair over 4 inches low at 300 yards. Using a 100-yard zero, POI is 15 inches below POA at that distance.
So, that’s how MPBR would work for a hunting rifle for, say, a hunter in the Western states where making longer shots at game is common compared to much of the rest of the US. Stalk to within 300 yards, and drop the hammer.
So what about MPBR for the typical carbine?
MPBR And Carbines
The typical person keeps a carbine/intermediate rifle for self-defense purposes and at that, really more for home defense, idle fantasies of dystopian futures aside.
Therefore, a target range of 8 inches is a bit too generous for precise placement, which usually wins gunfights.
The human heart is about the size of a fist, roughly a 4-inch circle. The human brain is not much bigger. So let’s say for the sake of discussion that a good combat MPBR would have a target area of 4 inches. What, therefore, is a good range to zero a carbine in, say, 5.56mm?
Typical 55-gr M193 (Green Tip isn’t a great choice for home defense!) has a BC of about .247 and a muzzle velocity of about 2900 fps from a 16.5-inch barrel. However, let’s also figure a 2.5-inch offset for the sights, typical for irons, LVPOs, and red dots on AR rifles.
As we can see, POI is 4 inches below POA, just before a distance of 225 yards. What about 200 yards?
At 200 yards, POI is just under 2 inches above POA at 125 yards and drops to 2 inches below POA at around the same distance of 225 yards.
Therefore, it would seem that 5.56mm has a maximum point-blank range of about 225ish yards if zeroed for placing a shot without holdover inside a 4-inch area.
Let us also consider another popular cartridge for a self-defense rifle, namely 7.62x39mm. The popular defense load is a 123-grain soft point, with a typical muzzle velocity of around 2300 to 2400 feet per second.
Using the 0.247 BC of Remington’s CoreLokt PSP in 7.62x39mm, and presuming a bore offset of 2.5 inches (say for a red dot on an Ultimak, railed sight block, or side mount), the MPBR shrinks dramatically.
For POI to be 2 inches above or below POA, the furthest you’ll get with 7.62x39mm is a hair over 200 yards. Granted, the Soviet method for zeroing AKs accounts for this (long story for another time), but you get the idea.
So What Is This MPBR Stuff Even Mean For Me And My AR?!
The idea here is that you can set your carbine to put a shot inside an area of a particular size out to a particular distance without having to hold over.
At CQB distances, you have to worry about bore offset, which is usually about 2.5 inches, but at – say – 25 yards out to whatever your MPBR is…you just put the dot or crosshairs on your target and squeeze.
That, and this is the key idea, makes getting hits easier. For a self-defense carbine or rifle, that means you basically won’t ever have to worry about holdover at most practical distances.
For a hunting rifle, the right load can mean never having to worry about holdover so long as your target is within your MPBR.
It isn’t necessarily the right thing for a precision rifle application, either for the target shooter or competitor. It means having to work up DOPE involving hold under and hold over, which makes things more complicated than you want them to be!
However, for any general-purpose do-it-all rifle…it’s a much more logical zeroing method than simply zeroing at 100 yards.
