Why an inch high at 100 yards???

Originally Posted By: BuckeyeSpecialwatch dog 80:

To answer your question: One poster here presented the acronym of MPBR but didn't explain its meaning = Maximum Point Blank Range.

That is MPBR is the range at which your bullet is no more than 2-3 inches above or below your crosshair, thus on a typical 270 such as yours sighted in to MPBR, the bullet will be almost on at 50 yards, 3 inches high at 100, 2 inches high at 200, and right on at say 250 and say 2-3 inches low at 300 yards ...[more or less].

This allows you to sight on a deer for instance and hit pretty much where you are sighting on the animal/target i.e. use the crosshair on the target, no need to hold high or low off the target. You just place the crosshairs on the animal anywhere from 0-300 yards and you will hit it.

Read up on MPBR in the loading manuals Exterior Ballistics section for various cartridges/animal sizes; it is a pretty effective and straightforward i.e. foolproof system, especially for big game hunting.

Close.

MPBR can be 2-3" for a 4-6" target. If your target is 18" you're looking at a 9" high/low range. The MPBR is the distance you can hold dead on without the bullet 'in theory' going above or below that target diameter. With a small target and rainbow gun that can be inside a 100 yards, with a large target and flat shooting caliber it can be 600 etc.

I shoot mpbr with all my hunting rifles. I haven't gone elk in quite a while but with the load I was shooting if memory serves, I was 4.7" high at 100 to give a 387 mpbr and ranging to 500 with minimal adjustment.

Using the identical load for goat the mpbr ranges in quite a bit since the target is only a 6" circle. The target size is a majority of what defines the end range.

AS for the OP, different calibers have different rules of thumb. 1" is really really generic and won't fit for a lot of calibers. Most modern high speed calibers won't drop a ton between 100 and 200 so it will more or less work for a lot.
 
NDIndy:

Please note my description of MPBR was provided as a general description in less than 200 words and wasn't intended to be perfect...thus my wording "more or less".

I also mentioned "...read up on MPBR" and mentioned "animal sizes".

Your point that "The target size is a majority of what defines the end range" is not so close in practical application i.e. one can set the 100 yard zero at 7 inches to make a large[er] kill zone at 500 yards on a large quarry (an elk) but that dies little to insure one will hit it in the optimum vital zone for a clean kill.

A MPBR of 7 inches at 100 yards does not make for a precisely placed shot at 60 yards, thus there are diminishing returns.

That is, I would nominate as more useful than an overly broad MPBR:

the skill level of the shooter past 300 yards;
shooter knowledge of trajectory;
energy level of the respective bullet at the maximum point blank range on the respective game animal targeted consistent with the Optimum Game Weight formula;
and that a 4 inch kill zone (target)is much more preferable to a 9 inch kill zone (target) to optimize humane killing.









 
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OK, I'm sure someone will correct me on this. However, it has always been my understanding that Maximum Point Blank Range was the "maximum" range the trajectory of the bullet got back to the "point blank" position.

For example; if the axis of the bore is 2" below the sighting point at the muzzle, (aka; point blank), then the MPBR would be where the trajectory once again put the impact of the bullet at the original point blank position.

This has absolutely nothing to do with the size of the target. Each load for any given caliber will have a set MPBR, depending on bullet bc, velocity, mass, and atmospherics, regardless of target size.

I guess I'm going to have to look this up.
 
The way MPBR was explained to me and the context I was originally using it was exactly as Jack explained it. If my target is a coyote, I can assume a 4" vital zone. If I were to center a 4" pipe on my barrel and shoot, I would adjust my sighting so the bullet would just graze the top of the pipe, and the MPBR would be the distance at which it fell back to the bottom of the pipe. So, in theory, you can put the crosshairs right in the middle of a coyote at any distance out to your MPBR and you should get a kill.

Like I said, I'm not comfortable with that. I prefer to sight in based on maximum assumed distance, which is often much less that MPBR, and here's why. Let's say the coyote at a 4" vital zone is the target. That means we can set 2" high. For my .243, that's at 170 yards, with a zero at 286, and an MPBR at 335ish. Anywhere from 0 to 335, I should be able to "hold on fur" and get the kill, right?

WRONG!!! Next time you are out in the field, find a object that is 335 yards out, and hold on it. You can't have a perfect hold at 335 in the field, not going to happen. Do the same thing at 170, and your crosshairs will bounce around. Can't hold perfect in the field.

So, if we can't hold perfect, we have to allocate for our inability to hold perfectly still. Say you have coyote at 170, and you hold on the fur. Just 1" of movement (and if you can hold 1" at 170 in the field, you're doing pretty good), means that now we could be 3"+ high. That my friends is a miss. Take that out to the 335 and you really better be rock solid...

Some people are comfortable setting up for MPBR, but I'm not. Like I said earlier, most of my shots are within 250 yards, so I can set up at 1" high at 100. That's a 180 yard zero, and 1.5 low at 220. Even if I move a little, I'm only dealing with 1" high/low out to my comfortable shooting range. Even with my crappy aim, I should kill a few...

 
The way it was explained to me is this. The targets vital size: say a deer has a vital size of 9 inches. So you have 4.5 inches above and below the midpoint. How far out can you extend a 9 inch diameter cylinder and keep the trajectory of the bullet within that 9 inches. That would be the MPBR of your rifle when shooting at a target/ animal with a 9 inch vital.

My 280 I can zero at 250 yards and keep the bullet within 4.5" above and below that point all the way to approx 325 yards. So my MPBR is approx 325 +/- for altitude, temp & baro pressure. I might even be able to adjust my zero and go out a little further if I play around with it a little more.
 
Originally Posted By: buckyne I might even be able to adjust my zero and go out a little further if I play around with it a little more.


You cannot adjust your zero to extend MPBR. If you change the zero, you are no longer inside the 4.5" high/low zone. Extending the MPBR is a product of your ballistics, so all things being equal, that's the only way to extend it is by improving that.
 
Basically, all the mumbo jumbo aside; 1" high is a rule of thumb. My dad was a gunners mate and did 20 years in the navy; he sets every gun he has for 1" high from his 7 rem mag to his 45-70 and 30-06. This works for him because he'll never shoot a deer past 150yrds. I was a scout in the army and I set all my shots to bullseye and use my ballistics calculator, CED M2 chrono and dope sheet for my guns. I prefer to shoot at much smaller targets much further away.
 
Originally Posted By: BuckeyeSpecialNDIndy:

Please note my description of MPBR was provided as a general description in less than 200 words and wasn't intended to be perfect...thus my wording "more or less".

I also mentioned "...read up on MPBR" and mentioned "animal sizes".

Your point that "The target size is a majority of what defines the end range" is not so close in practical application i.e. one can set the 100 yard zero at 7 inches to make a large[er] kill zone at 500 yards on a large quarry (an elk) but that dies little to insure one will hit it in the optimum vital zone for a clean kill.

A MPBR of 7 inches at 100 yards does not make for a precisely placed shot at 60 yards, thus there are diminishing returns.

That is, I would nominate as more useful than an overly broad MPBR:

the skill level of the shooter past 300 yards;
shooter knowledge of trajectory;
energy level of the respective bullet at the maximum point blank range on the respective game animal targeted consistent with the Optimum Game Weight formula;
and that a 4 inch kill zone (target)is much more preferable to a 9 inch kill zone (target) to optimize humane killing.

Post wasn't a slam on you^ and is just about the idea, not that advocacy of using every theoretical yard your round provides on a live target. Thus my "in theory"
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MPBR is NOT at all what I would recommend as precision anything and definitely doesn't take the place of knowing what you're doing. Just fast placement of an x sized target. The math stays the same regardless of practice (ethics). As with any hunting sighting/shooting within your ability and your rifles ability takes priority just like it does with precision shooting. That is if either me or my rifle is a 3moa shot, shooting at max mpbr is a really really really bad idea and both I and the animals are better served if I set a 100 yard zero and stay with it.

For me, the mpbr concept works well especially in my terrain where targets can vary from on my lap to over the horizon.

If you have a 12" vital and set your mpbr for an 8", there is substantially more room for error than if you're set for 12 and shooting at the far end of 12". So far in 15 years or so since I leaned the concept, it's served me well from 40 yards to almost 500 with just adjusting to vital size-2"/2. It has been basically 1 shot and the field dressing on everything from antelope (tiny) to elk (not so tiny), with mainly deer and goats since elk hunting is HARD and I'm lazy.

The easiest way I've explained it to people has been the 'shooting the pipe' scenario. The bigger the target, the bigger the pipe, the longer the pipe can be.


FWIW, my .223 is set 1" high at 100. Not a lot of play room on a prairie dog
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Hornady.com has a web page where you can easy calculate drop. Fill in your info and where you want to zero and hit the button. It is just a starting point. You can print the page and cut a cheat sheet to tape on your rifle or your scope flip up cover. Like I said it is a starting point.
 
This is all abunch of crap. Watchdog80 if you are 1 inch high with that load, You should be about dead on at 200 End of story.. I don't know what your problem is. nor does anyone else

Dave
 
Originally Posted By: BuckeyeSpecialwatch dog 80:

To answer your question: One poster here presented the acronym of MPBR but didn't explain its meaning = Maximum Point Blank Range.

That is MPBR is the range at which your bullet is no more than 2-3 inches above or below your crosshair, thus on a typical 270 such as yours sighted in to MPBR, the bullet will be almost on at 50 yards, 3 inches high at 100, 2 inches high at 200, and right on at say 250 and say 2-3 inches low at 300 yards ...[more or less].

This allows you to sight on a deer for instance and hit pretty much where you are sighting on the animal/target i.e. use the crosshair on the target, no need to hold high or low off the target. You just place the crosshairs on the animal anywhere from 0-300 yards and you will hit it.

Read up on MPBR in the loading manuals Exterior Ballistics section for various cartridges/animal sizes; it is a pretty effective and straightforward i.e. foolproof system, especially for big game hunting.

Sorry but that's not quite right either. When you sight in for MPBR that range will depend on nhow big you choose the target to be. If you choose a target of 6" dia then what will happen is that the bullet will never rise ove 3" above the line of sight and the MPBR will be where the bullet falls 3" below the line of sight. Think about shooting thru a dead straight 6" dia pipe. Line of sight is right down the center of the pipe and with a 6" target being used to figure MPBR, the bullet you fire will not hit the top or the bottom of the pipe untill MPBR is reached. The trajectory of any bullet from any firearm can be adjusted to the size of the target. The idea is to be able to hold on a target at some range and not shoot over it or under it till MPBR is reached.
 
Originally Posted By: Don Fischer

Sorry but that's not quite right either. When you sight in for MPBR that range will depend on nhow big you choose the target to be. If you choose a target of 6" dia then what will happen is that the bullet will never rise ove 3" above the line of sight and the MPBR will be where the bullet falls 3" below the line of sight. Think about shooting thru a dead straight 6" dia pipe. Line of sight is right down the center of the pipe and with a 6" target being used to figure MPBR, the bullet you fire will not hit the top or the bottom of the pipe untill MPBR is reached. The trajectory of any bullet from any firearm can be adjusted to the size of the target. The idea is to be able to hold on a target at some range and not shoot over it or under it till MPBR is reached.

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That is how I read it in one manual. And it works.

Don DAB
 
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