300 yard zero???

Biggfoot44 said:

Post #9 and post #10 lay out the dueling philosophies back to back . And my take is ... not exactly either .

My disagreement with the maximum point blank theory is its putting equal value upon holding under at more frequent distances, and hold over at longer distances . I despise hold unders , and accept reasonable hold overs .

Click to expand...

The idea of MPBR is NO hold over or under. You aim center of vital area, and the bullet will strike within the vital area.

So MPBR does change with type of target. So for a target with a 10" diameter vital area, the MPBR would be such that a center hold would impact no more than 5" high or 5" low from the muzzle to the MPBR max range. Beyond that max range, you would have to hold over.

There would never be a hold under using MPBR.

Hawkeye said:

Thanks, Ed. I actually knew the math for the radian. The radian *IS* the SI unit of angular measure (it is technically an SI Derived Unit, since it is calculated based on the SI base units, but it is the SI measure of angle), and the miliradian is another derived unit that comes from the radian.

You're correct that it is based on the mathematical properties of the circle, but it's the SI unit of angular measurement.

Click to expand...

The point is, SI adopted the radian, but it is not inherently SI.

It existed before there were SI units. And were used by the US military when they exclusively used Imperial units.

E.Shell said:

In combat situations, there is no time to think or dial. The customary 400 yard zero for a scoped .308 provides for instant action with the widest possible range capability for that load. If a target pops up at 100 yards, indicating great urgency in response, you need only hold 2.4 mils low of your desired impact point. 2.4 mils at 100 is only 8-1/2", so a belt buckle hold gets a center hit. If a target pops up at 700 yards, you need to hold up 3.9 mils, well within your 5 mil holdover span (customary mildot reticle), so you can react quickly with a simple holdover.

Click to expand...

Why would you not use a MPBR zero for that use?

Or actually, what I would do, is zero for 100 yards, then dial the scope for the MPBR setting, and be set.

SO for my .308 load, the MPBR is 321 yards with a 273 yard zero.

So with my 100 yard zero, I would dial in 1.2 mil and would be hold center of vital area from the muzzle to 321 yards. Beyond 321 yards, I would have to dial a new setting or hold over.

E.Shell said:

Thanks Hawkeye.

While the Meter is indeed an SI unit,a radian is not listed.

Click to expand...

This is going to be a tangent (ha, ha, see?) from the original thread, but its an interesting discussion, so:

SI has two kinds of units, Base Units and Derived Units.

Base Units are the basic set of seven units from which other SI units are derived. They are the metre, kilogram, second, ampere, kelvin, mole, and candela. They're defined in different ways, (and those definitions have changed over time - the one you quoted about Paris and the North Pole is old, for example, and the current definition of a metre is the length of the path travelled by light in vacuum during a time interval of 1 / 299792458 of a second) and they are generally defined around some observable property of nature.

Derived Units are an additional set of units that are generally derived from one of the seven Base Units (like the lumen, which is derived from the candela). There are a ton of these. Some of them, like the radian, used to be classified as "Supplemental Units," but they got rid of that designation a while ago and lumped them all in as Derived Units.

The radian is the official SI unit of angular measure. It is a Derived Unit because you would do the math in meters in SI. It is, like you said, based on the physical principles of a circle, but it's one of several ways of measuring and quantifying those physical principles (MoA is another one, so is the Gon). It just happens to be the one that was chosen as the official measurement for the SI system because (among other reasons) as you observed it uses base 10 math and works well with the rest of SI.

I hope that makes some kind of sense. I was much more "up" on all of this years and years ago when I did my BS in Biology and everything we did was SI.

Pinecone said:

The point is, SI adopted the radian, but it is not inherently SI.

It existed before there were SI units. And were used by the US military when they exclusively used Imperial units.

Click to expand...

Units of measure aren't inherently anything - they're an invented way to measure stuff. There are a bunch of ways to do angular measure, and the radian was formally defined and named by several guys (James Thompson, the brother of Lord Kelvin and Thomas Muir) in roughly the 1870s.

In any case, the Radian IS the official SI unit of angular measure.

Pinecone said:

The point is, SI adopted the radian, but it is not inherently SI.

It existed before there were SI units. And were used by the US military when they exclusively used Imperial units.

Click to expand...

Thank you.

Pinecone said:

Why would you not use a MPBR zero for that use?

Click to expand...

"Ours is not to wonder why, but to do or die."

One word explanation: Doctrine.

Hawkeye said:

This is going to be a tangent (ha, ha, see?) from the original thread, but its an interesting discussion, so:

Click to expand...

Ugh...

SI has two kinds of units, Base Units and Derived Units.

Base Units are the basic set of seven units from which other SI units are derived. They are the metre, kilogram, second, ampere, kelvin, mole, and candela. They're defined in different ways, (and those definitions have changed over time - the one you quoted about Paris and the North Pole is old, for example, and the current definition of a metre is the length of the path travelled by light in vacuum during a time interval of 1 / 299792458 of a second) and they are generally defined around some observable property of nature.

Click to expand...

I understand the convention, and yes, the comparison to light in a vacuum is indeed more precisely expressed and different than the French meridian stuff, but I was trying to find a way to actually relate the length of a meter to circle math, so it really could BE metric, but alas...

Derived Units are an additional set of units that are generally derived from one of the seven Base Units (like the lumen, which is derived from the candela). There are a ton of these. Some of them, like the radian, used to be classified as "Supplemental Units," but they got rid of that designation a while ago and lumped them all in as Derived Units.

Click to expand...

Certainly the Radian is an important concept and worthy of inclusion, but the earlier assertions were that the Radian is a unit of metric measure, i.e.: "Metric".

The radian is the official SI unit of angular measure. It is a Derived Unit because you would do the math in meters in SI.

Click to expand...

So, it's really NOT metric, but because the rest of the SI is expressed in metric, it is metric by association? OK, that clears things up.

It is, like you said, based on the physical principles of a circle, but it's one of several ways of measuring and quantifying those physical principles (MoA is another one, so is the Gon). It just happens to be the one that was chosen as the official measurement for the SI system because (among other reasons) as you observed it uses base 10 math and works well with the rest of SI.

I hope that makes some kind of sense. I was much more "up" on all of this years and years ago when I did my BS in Biology and everything we did was SI.

Click to expand...

Thank you for your explanation. I do understand how the radian came to be a derived SI value and came to be expressed in meters.

"Expressed in meters" due to association with SI seems quite a far cry from actually being a metric measurement, based on some sort of actual metric value. It is clearly a ratio that can express, or be expressed, in numerous ways.

Units of measure aren't inherently anything - they're an invented way to measure stuff. There are a bunch of ways to do angular measure, and the radian was formally defined and named by several guys (James Thompson, the brother of Lord Kelvin and Thomas Muir) in roughly the 1870s.

In any case, the Radian IS the official SI unit of angular measure.

Click to expand...

Thank you, I agree it is used as an SI unit.

I'm still trying to see the logical formula that demonstrates that it is a metric value.

Honestly I think I shot myself in the foot when I said "Metric" in my first post about it, because it's not a "metric" measurement in that way. I should have been more careful about my wording. I often use "metric" when I am talking about "SI" because a lot of people equate the two and it often makes good shorthand, especially when non-nerdy people aren't familiar with SI, what it is, and how it's set up.

Basically, SI (from the French, Système international d'unités, so it's really "IS" for International System if we abbreviated it in English...) is basically a "modern metric system." It was invented because scientists and engineers were realizing that to get any work done in a global world, they needed a standard set of units that everyone could use and were all agreed upon and easily referenced. When they built it, they started with the metric system as the source of a lot of the base units because a) the metric system was in use a lot of places and b) the units in metric tended to be based off of repeatable, observable physical phenomena (scientists like that!) instead of the size of the King's foot or his thumb or how many links were in a chain (I worked as a land surveyor, don't get me started) or whatever. Plus, base 10 math is easier for most people to do than a system where some things are multiples of 12, but others are multiples of 8, and a pint in the USA is different than a pint in the UK, etc.

So yeah, you're correct, it's not technically a "Metric" measurement, but an SI one.

Also in my own defense, my original post did say

Mils are a measure of angle, just like MoA (minutes of angle). It's just an SI (metric) measure instead of an English one.

Click to expand...

See? I even had "metric" in parenthesis.

Honestly, thanks for being so good natured about it, and now our tangent can return to the origin....

“Mils are a measure of angle, just like MoA (minutes of angle). It's just an SI (metric) measure instead of an English one. You can calculate holdover / holdunder in either system. Some reticles are set up with mildots (i.e. they measure in mils, or miliradians), and some are in MoA or other measures. Some have BDCs, or bullet drop compensators, which are generally set up for a specific load out of a specific barrel length and a specific zeroing distance. Then you just range your target and put the appropriate point in the reticle on it and shoot.

If you know what your'e doing you can calculate a hold no matter which type of reticle you have.”

I understand this. I was asking the poster what reticle he was referring to. I have some from the ensuing posts.

Otherwise...good thread

You guys are overthinking this w-a-a-a-y-y-y too much.

The guy in the show was just showing where the bullet would hit if he zeroed at 300 yards then he shot targets at 50, 100, 200 and 300 yards. It made sense when he showed where the bullets hit. Another guy used a 100 yard zero and he was way off on the 300 shot.

He said that is you wanted to take a 400 yard shot then just aim at the top of the animal's back.

I run both MOA and MRAD scopes... I get confused sometimes.

Striper69 said:

You guys are overthinking this w-a-a-a-y-y-y too much.

The guy in the show was just showing where the bullet would hit if he zeroed at 300 yards then he shot targets at 50, 100, 200 and 300 yards. It made sense when he showed where the bullets hit. Another guy used a 100 yard zero and he was way off on the 300 shot.

He said that is you wanted to take a 400 yard shot then just aim at the top of the animal's back.

Click to expand...

But why not use Maximum Point Blank Range?

Then you have a known range where you don't have to worry about any hold over and under.

Making up something that is not as good as something already out there.

I have zeroed my 300 Win Mag and 7MM Rem Mag rifles at 300 yards. Now I'll shoot them at 50, 100, and 200 yards to see where they hit. He was using a 6.5 Creedmore though. I tried to zero my 6.5 Creedmore but the frickin' scope I tried to use kept going out of adjustment so I'm going to use a new scope I bought.

Pinecone said:

But why not use Maximum Point Blank Range?

Then you have a known range where you don't have to worry about any hold over and under.

Making up something that is not as good as something already out there.

Click to expand...

I think his point was that he didn't have to use holdover or holdunder.

The segment was about setting up the 6.5 Creedmore for hunting.

That is the point of Maximum Point Blank Range.

No hold under or over from muzzle to X range. Applies to ALL calibers (range differs) and any target (range varies based on difference in vital area size).

I agree with Pinecone. There is no reason not to use a Max Point Blank Range zero for any caliber. Any distance that it wouldn't work to put point of aim directly on the target and expect point of impact to put meat in the freezer is getting to unethical hunting ranges anyway...unless you're a very accomplished rifleman, in which case a holdover or a turret adjustment isn't going to be a problem.

But to each their own.

I think you're talking about the same thing but you guys are trying to put a fancy name to it and complicate it.

No, we are trying to make a specific process to accurately do what this WAG sort of does.

There is one range to zero at and one maximum range, that a given load will hit within a certain distance from the point of aim.

The fact that this method tells you to shoot at various distances to figure out hold under, means it is making more work for you.

And not complicated, put your load info in JBM Ballistics online, tick the MPBR checkbox, run the calcs, and get the answer.

And using JBM, it tells you what the POI will be at various ranges, so you can zero your rifle without having a target at the proper range. Just adjust impact X high at 100 yards or Y high at 200, or whatever.

Using the Wiki data for 6.5 Creedmore (Hornady 143 gr ELD-X at 2710 FPS), and a sight height of 1.9" (my rifle), the Max Point Blank Range (10" vital zone) is 342 yards, with a zero at 290 yards.

To set this, you would set your rifle to shoot 4.0" high at 100 yards or 4.5 inches high at 200 yards. Or 0.8 inches low at 300 yards.

NO hold over and under required.

Striper69 said:

I think you're talking about the same thing but you guys are trying to put a fancy name to it and complicate it.

Click to expand...

Not quite.

One school of thought is saying to zero at a set range, and know your hold overs. Then adjust your point of aim based on the range you estimate the target to be. The goal is to have your point of impact land exactly where you want it to, although precision is generally elusive with Kentucky windage. With different reticles and practice you can get pretty good though and it's pretty fast.

Another school of thought is to zero at a set range, and adjust your turrets (if you have adjustable turrets) to adjust your reticle so that your point of aim equals your point of impact. Here precision is the goal. You need to know the ballistics for that load, and have a really good range estimation. It takes time, it's very slow relative to the other approaches, but with practice also very precise.

The MPBR is a different approach. You set your zero for the distance where the bullet's trajectory will rise / fall above or below the point of aim within an acceptable measurement. About 4 inches above / below, which gives you about 8 inches of impact zone (or in military terms cone of fire)...enough to hit a 8-10" vital area. When engaging a target, the shooter doesn't need to adjust their point of aim and "hold over," they just always aim center of the vital area and shoot. It's not precision we're going for, but looking to put meat in the freezer. It's very fast, and not at all precise...but precise enough to get the results we're looking for.

What's the right approach. All of them Depends on the goals of the shooter and what they are comfortable with.

For me, I hate holdovers and BDC reticles (or turrets). It seems like a compromise between speed and precision that doesn't do either particularly well.

Rifles that I like to shoot small groups on a range with, I generally zero at 100 yds and develop trajectory charts for each load with come ups to adjust the turret.

For my hunting rifle and things more HD related, I use the MPBR approach.

And to Pinecone's point, figuring out the distances where your bullet rises / falls below your point of aim within the cone that is acceptable to you is very easy now-a-days with online ballistics calculators. Just plug in the variables and it'll tell you what you need to know.

OP doesn't explicitly state what caliber or weapon they are using or intended purpose . To that ends what type of zeroing technique is appropriate remains a guess. OP if the technique you watched seems to fit your needs then by all means try it out. the worst thing that could happen is you will need to try a different technique later.