Formidilosus
Super Moderator
- Joined
- Oct 22, 2014
- Messages
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Zeroing for maximum point blank range is quite often offered as a good way to zero to eliminate “thinking” when an animal steps out. Seems simple enough- zero a rifle at a range that the bullet doesn’t rise above a predetermined height, and when it falls below line of sight at that same distanc; that is your MPBR.
For instance-
300 Win Mag, 190gr Sierra, 2950fps MV.
Set for an 8” target (deer) we have a MPBR of 320’ish yards. Zeroed at 285yds, the bullet will be just under 3” high at 100, hit right at 4” high at 175 or so, dead on at 285, and 4” low at 320.
Sounds good, right? Aim in the middle and don’t worry about range from muzzle to past 300 yards.... Except when actually tested- misses happen. Quite often, actually. Now, there will be a bunch of people saying “works for me” or been doing it for 20 years”, and it does work. Usually. Of course most people tend to forget when they miss as well. But when actually taken to a range with a case of ammo and zeroed exactly as above and shot off a rest at random distances from contact to 320 yards; that setup above will have around a 70-75% hit rate on that 8 inch target. In other words- 25-30% of shots miss, especially between 150-200 yards and again 290’ish to 320 yards. This is reality, it’s been tested a lot.
Why? Well the major cause is group size. The trajectory calculations are for a point. Rifles don’t shoot to a “point”, they shoot in a “cone”. So our 4 inch high or low is to the center of the cone. What about the 50% of shots that are above and below the center of the cone? Combine group size with maximum ordinate (4”) and 4” of drop at 320, and you get quite a few misses.
In fact, between 150-200 yards and 300-320 yards you’ll have a 50% hit rate or less if you hold dead center.
Today we were working with AB Analytics on WEZ (weapon employment zone), I.e.- hit rates given a certain sets of parameters. Not to have a long conversation of how it works, but it “fires” a 1,000 shots randomly with those parameters and plots each one. It very accurately models reality.
A couple of us got to talking about MPBR as well as hunting so we ran the WEZ for it. Given standard conditions, good ammo, 2 MOA precision (which is realistic in the field) and the above combination (300WM, 190gr Sierra, 2,950fps) and an 8” zone-
MPBR results in just over a 70% hit rate.
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You can see in this graph why it’s happening. Right about 150 yards the hit rate starts dropping. The Max Ord and group size is beginning to hurt us.
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Now compare that with aiming dead on at 320 yards with the exact same rifle and conditions-
99.9%
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Should be pointed out that inside of 310 yards it is a 100% hit rate...
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I’ve stated before on the form that MPBR doesn’t work as well as people think, and have gotten into a couple heated discussions about it. Yes, you can kill a deer doing it. Maybe even a few. But if you shoot at enough of them, you will see misses that shouldn’t have happened. This is why.
* A couple of caveats- it’s not exact as the program wasn’t designed for specifically doing MPBR. However it is VERY close, as in- within a few percentage points on the low end. It also matches what I’ve/we’ve seen every time we’ve tested it.
For instance-
300 Win Mag, 190gr Sierra, 2950fps MV.
Set for an 8” target (deer) we have a MPBR of 320’ish yards. Zeroed at 285yds, the bullet will be just under 3” high at 100, hit right at 4” high at 175 or so, dead on at 285, and 4” low at 320.
Sounds good, right? Aim in the middle and don’t worry about range from muzzle to past 300 yards.... Except when actually tested- misses happen. Quite often, actually. Now, there will be a bunch of people saying “works for me” or been doing it for 20 years”, and it does work. Usually. Of course most people tend to forget when they miss as well. But when actually taken to a range with a case of ammo and zeroed exactly as above and shot off a rest at random distances from contact to 320 yards; that setup above will have around a 70-75% hit rate on that 8 inch target. In other words- 25-30% of shots miss, especially between 150-200 yards and again 290’ish to 320 yards. This is reality, it’s been tested a lot.
Why? Well the major cause is group size. The trajectory calculations are for a point. Rifles don’t shoot to a “point”, they shoot in a “cone”. So our 4 inch high or low is to the center of the cone. What about the 50% of shots that are above and below the center of the cone? Combine group size with maximum ordinate (4”) and 4” of drop at 320, and you get quite a few misses.
In fact, between 150-200 yards and 300-320 yards you’ll have a 50% hit rate or less if you hold dead center.
Today we were working with AB Analytics on WEZ (weapon employment zone), I.e.- hit rates given a certain sets of parameters. Not to have a long conversation of how it works, but it “fires” a 1,000 shots randomly with those parameters and plots each one. It very accurately models reality.
A couple of us got to talking about MPBR as well as hunting so we ran the WEZ for it. Given standard conditions, good ammo, 2 MOA precision (which is realistic in the field) and the above combination (300WM, 190gr Sierra, 2,950fps) and an 8” zone-
MPBR results in just over a 70% hit rate.
You can see in this graph why it’s happening. Right about 150 yards the hit rate starts dropping. The Max Ord and group size is beginning to hurt us.
Now compare that with aiming dead on at 320 yards with the exact same rifle and conditions-
99.9%
Should be pointed out that inside of 310 yards it is a 100% hit rate...
I’ve stated before on the form that MPBR doesn’t work as well as people think, and have gotten into a couple heated discussions about it. Yes, you can kill a deer doing it. Maybe even a few. But if you shoot at enough of them, you will see misses that shouldn’t have happened. This is why.
* A couple of caveats- it’s not exact as the program wasn’t designed for specifically doing MPBR. However it is VERY close, as in- within a few percentage points on the low end. It also matches what I’ve/we’ve seen every time we’ve tested it.