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I can totally understand that environmental conditions, twist, etc can change the bc. But it would be nice if there were a industry standard for measuring/ advertising bc's. That way we could make a direct comparison from manufacturer to manufacturer.



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Originally Posted by RaySendero
Axtell, My hat's off to you! Your patience seems endless!


That's not patience. Axtell went from implying that his BC calculations were more accurate than Litz's to admitting that they were not.

The fact that it took him several posts to backpedal is not patience, it's arrogance.

Axtell is also the guy who touts the fact that he weighs his powder charges using a jeweler's scale to the nearest 0.02 grain, and claims that this makes a difference.

I have no patience for such claims.

Fred's orientation notwithstanding.



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Rabbit trail maybe, but all this talk about minutia, % of difference here and there, but I never hear anyone talk about how the rifling deforming the bullets smooth slippery surface changes BC. Seems like that'd change everything.


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Jordan pointed that out a few posts back.



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Originally Posted by Axtell
^^^ BC's are, from manufacturer's, are a comparative value, this bullet higher/lower than that one.

With the LabRadar, which gives velocities at several user determined distances, you can calculate the actual BC for your elevation and environmental conditions. From actual bullet drops.

I use Litz's BC's to get in the ball park, they are actually pretty close.



Smokepole

You are reading this initial post incorrectly. You are presuming that you can take a listed BC plunk it into a ballistic program and get 'advertised results'.

The above statement clearly states that I use Litz's BC's, as they are the best available, as there is no bias to marketing by a manufacturer.

Now using Litz's BC's do get you in the ballpark, but sometimes require fine tuning (for your particular circumstance)as laid out in subsequent posts.

There is no back peddling on my part. Only time spent in an effort to understanding. You seem to have your mind made up, so I guess it was a waste of time, my bad.

You have had a hard on for me since I questioned your buddy H-22 about his Ruger blowing up. The line of questioning was hard but sometimes that is what is necessary to uncover the sequence of events that caused the incident.

Weighing powder: consistency is the grail in producing good ammunition, weighing powder to the nearest 0.02 of a gr takes no more time than weighing to the nearest 0.1gr on a balance beam scale, so why not. Further, measuring seating depth or COL is more accurate with a vernier than a yard stick. Most would grasp this idea.

The arrogance smoke screen is just one that tells me that you do not understand these basic concepts......therefore reject them, as you have no ammo for debate.


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Axtell,

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weighing powder to the nearest 0.02 of a gr takes no more time than weighing to the nearest 0.1gr on a balance beam scale, so why not.


What kind of powder do you use and how much does one granual weigh?


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With all these measurement discussions, there is a level of resolution within which a material difference in results can be observed. Remember Sig Dig's? Significant digits- greater resolution adds no greater significance to the data. This is to say that measuring cartridge BTO length to within 0.0001" has no observable impact on results, just as measuring powder charge to within 1 granule has none, nor does calculating BC values to 0.0001.

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Originally Posted by Axtell


Smokepole

You are reading this initial post incorrectly. You are presuming that you can take a listed BC plunk it into a ballistic program and get 'advertised results'.


I'm presuming nothing, just reading what you wrote. When you say someone else's numbers are "pretty close" you're saying the numbers are good, but could be better.

In other words, you're saying Litz's numbers are close but not right on.

The only way you can know that is if you have better numbers, and that's what your statement implies.

Which is nonsense.

And that BS you were directing at Huntsman has nothing to do with it. I just think you're FOS.



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H-4350, Varget, H4895 and H-1000 weigh ~0.02 of a grain per kernal. I mostly use these powders. The finer/denser extruded powders like VV N-550, to a lesser extent RL-17 are harder to get +/- one kernel.

My scale only resolves to 0.02gr so any weights I get are within this parameter.

It took me some time to develop a technique that gave accurate results in a timely manner.

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Originally Posted by smokepole
Originally Posted by Axtell


Smokepole

You are reading this initial post incorrectly. You are presuming that you can take a listed BC plunk it into a ballistic program and get 'advertised results'.


I'm presuming nothing, just reading what you wrote. When you say someone else's numbers are "pretty close" you're saying the numbers are good, but could be better.

In other words, you're saying Litz's numbers are close but not right on.

The only way you can know that is if you have better numbers, and that's what your statement implies.

Which is nonsense.

And that BS you were directing at Huntsman has nothing to do with it. I just think you're FOS.



BC's will vary somewhat due to as stated previously twist rate, environmentals and in addition the degree of 'damage' the bullet gets as it enters the rifling all play a part.

There are no better numbers ......just numbers that jive with reality of bullet drop.

I won't go into the effects of refraction, probably a waste of time in this conversation.

Depending on your shooting discipline, whether it is hunting deer at near ranges, varmints at long range or 1000 yard competition, will dictate the level performance required for success.

Its better to have a high level of performance and not need it than the other way around.


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Originally Posted by Jordan Smith
With all these measurement discussions, there is a level of resolution within which a material difference in results can be observed. Remember Sig Dig's? Significant digits- greater resolution adds no greater significance to the data. This is to say that measuring cartridge BTO length to within 0.0001" has no observable impact on results, just as measuring powder charge to within 1 granule has none, nor does calculating BC values to 0.0001.


I agree, there is a point where effort and reward are immeasurable.

But, do not abandon good practice, try to keep things tight, the reward is consistency.

With the tools available today there is less effort and greater reward than has been previously known.

I see this in group sizes shrinking and the probability of a hit increasing.

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Originally Posted by Axtell

BC's will vary somewhat due to as stated previously twist rate, environmentals and in addition the degree of 'damage' the bullet gets as it enters the rifling all play a part.


Yes, that much is clear and it's been stated by a few different posters already so there's no need to repeat the obvious.

It doesn't lend any credence to your posts, all it does is show how ridiculous it was for you to say that someone else's numbers were "pretty close."



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A bullet's BC is independent of atmospherics, the atmospherics are entered in a ballistics solver to obtain density of air and speed of sound not to change the BC of a bullet. Please read this book if you are in doubt about the BC's independence of atmospheric conditions.

I am not saying that atmospheric conditions do not change the trajectory because it does because the denser the air is the greater the drag is, assuming both bullets are the same and have equal speeds.

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^^^

When punching info into the Ballistic program, all known parameters, the variables are mainly elevation and environmentals.

So, in the program to get an accurate drop prediction what changes..........its the effective BC of the bullet.

To say a BC of a bullet is x.xxx is most likely a reference to a standard.

Does it make a lot of difference , not likely , but it gives an understanding of what is happening.

Or , one could defend a position with walls made of words that include arrogance, BS, ridiculous, the obvious which probably is delivered with a huge eye roll.

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Originally Posted by Axtell

Or , one could defend a position with walls made of words that include arrogance, BS, ridiculous, the obvious which probably is delivered with a huge eye roll.


I'm pretty sure you deliver all of that with a straight face.



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Originally Posted by smokepole
Originally Posted by Axtell

Or , one could defend a position with walls made of words that include arrogance, BS, ridiculous, the obvious which probably is delivered with a huge eye roll.


I'm pretty sure you deliver all of that with a straight face.


Pretty much, trying to keep from slipping into Alaska trailer park ghetto talk. Have yourself a good day and shoot straight.

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Originally Posted by smokepole

Axtell is also the guy who touts the fact that he weighs his powder charges using a jeweler's scale to the nearest 0.02 grain, and claims that this makes a difference.

I have no patience for such claims.




Had a discussion with one of the Nation's top PRS shooters about this very subject. He's been weighing charges to the granule and has seen SD's for strings of 30 rounds reduced to 8



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Originally Posted by rcamuglia
Originally Posted by smokepole

Axtell is also the guy who touts the fact that he weighs his powder charges using a jeweler's scale to the nearest 0.02 grain, and claims that this makes a difference.

I have no patience for such claims.




Had a discussion with one of the Nation's top PRS shooters about this very subject. He's been weighing charges to the granule and has seen SD's for strings of 30 rounds reduced to 8



OK, but can any improvement from this be reliably resolved on target?

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Originally Posted by mathman
Originally Posted by rcamuglia
Originally Posted by smokepole

Axtell is also the guy who touts the fact that he weighs his powder charges using a jeweler's scale to the nearest 0.02 grain, and claims that this makes a difference.

I have no patience for such claims.




Had a discussion with one of the Nation's top PRS shooters about this very subject. He's been weighing charges to the granule and has seen SD's for strings of 30 rounds reduced to 8



OK, but can any improvement from this be reliably resolved on target?



Which brick do you take out of a wall that allows the whole structure fall apart ?

I will not knowingly degrade my standards to the Lee powder dipper method, which btw are pretty good for hunting grade ammo inside 200 or so yards.


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Originally Posted by Axtell
^^^

When punching info into the Ballistic program, all known parameters, the variables are mainly elevation and environmentals.

So, in the program to get an accurate drop prediction what changes..........its the effective BC of the bullet.

To say a BC of a bullet is x.xxx is most likely a reference to a standard.

Does it make a lot of difference , not likely , but it gives an understanding of what is happening.

Or , one could defend a position with walls made of words that include arrogance, BS, ridiculous, the obvious which probably is delivered with a huge eye roll.


Not exactly. The only thing that the ballistic calculator is figuring out WRT environmentals, is how dense is the air that the bullet is flying through, or in other words how much aerodynamic drag is the bullet experiencing in flight. Elevation is irrelevant if you know the pressure and temperature, or just the density, of the air at your firing position.

The BC is a measure of how aerodynamic a given bullet is compared to a standardized bullet. Environmental conditions don't change that, since they apply equally to all bullets, they simply increase the level of resistance that the bullet has to overcome.

The BC is simply expressed by form factor, or bullet shape, and SD. Rifling engraving changes the shape, and therefore changes the form factor. Environmental factors don't alter the BC of a bullet directly, but I see what you're saying that they indirectly affect the bullet's flight characteristics.

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