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Re: POI of heavier vs. lighter bullets [Re: P_102] #8143519 01/26/21 01:17 AM
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Originally Posted by P_102
“It's true that all other things held equal, a higher velocity bullet will impact higher at long ranges. “

“ It doesn't even matter what distance you're zeroed for. 100% the slower bullet will shoot higher.“

Um, Hick.....which is it?



Please reread what ranges I'm talking about in my paragraphs.

Re: POI of heavier vs. lighter bullets [Re: HicksHunter] #8143561 01/26/21 01:48 AM
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I never said or implied I am the only one with experience. You're basing your argument off of theory instead of range time, and actually shooting. If you've got the real world experience, lead with that.

There's a whole lot of people around here that have seen my real data.

Close range, bullets rise to the 100 yard zero. The bullet path intersects at the POA on a well zeroed scope. After 100 yards the bullet is falling, period. Seen it with velocity spreads over 2500 fps different, up to 3400 fps MV. The ballistic calculator has no place inside of 100 yards for a center fire rifle round. Case in point, "The MOA Walk Back." Start at 7 yards, and hit a 1 MOA dot. Back up to 17 yards, 27, 37, 47, all the way to 77 yards. Plug in a scope height to the .01", plug in bullet weight, BC, MV and ask the calculator what the corrections are. Ask more than one calculator and you'll get a difference every time. And none of them are correct. Why? It is all theoretical. Only way to get close in DOPE is like any other DOPE, Data On Previous Engagement, ya gotta shoot it for real. Lost 8 out of 10 points the first time I encountered it. The next month, I cleaned it, because I had shot it at my home range.

Shooting at 50 and 100 yards for two different MVs is going to yeild the exact results I expect. I expect it because I have already done it. .223, .223 A.I., .22-250, .243, 6.5 Creedmoor, 7mm-08, 7mm-08 A I. .308, 7 Rem Mag. Every one of them a different MV, every one of them a different bullet (Except the 7mm-08s), every one of them a different MV. Zeroed at 100 yards, .4 or .5 Mil at 50 yards. .3, .4, or .5 Mil at 200 yards.


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Re: POI of heavier vs. lighter bullets [Re: onlysmith&wesson] #8143581 01/26/21 01:59 AM
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You realize there is an ammo and reloading sub-forum a couple spots down from this firearm discussion sub-forum, correct?


Pass the gravy.


Re: POI of heavier vs. lighter bullets [Re: FiremanJG] #8143597 01/26/21 02:20 AM
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Originally Posted by FiremanJG
I never said or implied I am the only one with experience. You're basing your argument off of theory instead of range time, and actually shooting. If you've got the real world experience, lead with that.

There's a whole lot of people around here that have seen my real data.

Close range, bullets rise to the 100 yard zero. The bullet path intersects at the POA on a well zeroed scope. After 100 yards the bullet is falling, period. Seen it with velocity spreads over 2500 fps different, up to 3400 fps MV. The ballistic calculator has no place inside of 100 yards for a center fire rifle round. Case in point, "The MOA Walk Back." Start at 7 yards, and hit a 1 MOA dot. Back up to 17 yards, 27, 37, 47, all the way to 77 yards. Plug in a scope height to the .01", plug in bullet weight, BC, MV and ask the calculator what the corrections are. Ask more than one calculator and you'll get a difference every time. And none of them are correct. Why? It is all theoretical. Only way to get close in DOPE is like any other DOPE, Data On Previous Engagement, ya gotta shoot it for real. Lost 8 out of 10 points the first time I encountered it. The next month, I cleaned it, because I had shot it at my home range.

Shooting at 50 and 100 yards for two different MVs is going to yeild the exact results I expect. I expect it because I have already done it. .223, .223 A.I., .22-250, .243, 6.5 Creedmoor, 7mm-08, 7mm-08 A I. .308, 7 Rem Mag. Every one of them a different MV, every one of them a different bullet (Except the 7mm-08s), every one of them a different MV. Zeroed at 100 yards, .4 or .5 Mil at 50 yards. .3, .4, or .5 Mil at 200 yards.


Try the experiment I suggested and report back. I'll buy you a beer next time you drive through New Braunfels if I'm wrong.

Re: POI of heavier vs. lighter bullets [Re: HicksHunter] #8143626 01/26/21 02:45 AM
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Originally Posted by HicksHunter


It's true that all other things held equal, a higher velocity bullet will impact higher at long ranges.




This is not true at all

Last edited by cowie14; 01/26/21 02:46 AM.
Re: POI of heavier vs. lighter bullets [Re: onlysmith&wesson] #8143628 01/26/21 02:48 AM
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I've done ladder tests at 300 yards where the faster loads (same weight) shoot lower than the slower loads. The answer is harmonics. Any time you change anything (bullet weight, pressure, speed, charge, adding/removing muzzle brake or suppressor, sometimes just changing the stock or action screw torque, etc.), the barrel will act differently. The goal of handloading is to find the spot in the harmonics that is most forgiving and allows for the smallest variance in output.

Re: POI of heavier vs. lighter bullets [Re: onlysmith&wesson] #8143636 01/26/21 02:58 AM
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Positive compensation, that is the word you are looking for. Alex Wheeler knows more about it than anyone especially at 1k

http://www.geoffrey-kolbe.com/articles/rimfire_accuracy/tuning_a_barrel.htm

Here is an example at 600 yds:

42.4 2776fps
42.5 2786
42.8 2786
42.9 2805

not sure the group but maybe 1.25"

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Last edited by cowie14; 01/26/21 03:04 AM.
Re: POI of heavier vs. lighter bullets [Re: HicksHunter] #8143655 01/26/21 03:23 AM
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Originally Posted by HicksHunter
Originally Posted by P_102
“It's true that all other things held equal, a higher velocity bullet will impact higher at long ranges. “

“ It doesn't even matter what distance you're zeroed for. 100% the slower bullet will shoot higher.“

Um, Hick.....which is it?



Please reread what ranges I'm talking about in my paragraphs.


Both of those statements discount ranges altogether, especially when you start throwing around 100%.


Do not trifle in the affairs of dragons, for thou art crunchy and taste good with ketchup.
Re: POI of heavier vs. lighter bullets [Re: onlysmith&wesson] #8143659 01/26/21 03:26 AM
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Hickshunter, you are plugging those numbers into an online calculator. That online calculator is asking about your zero distance, right? As you are changing velocity, but not changing your zero distance, the calculator is angling the barrel up to compensate for the difference in drop. That's why your numbers are wrong. Try the calculator with a zero distance of zero. Then you will see that the heavier bullet will drop faster and print lower based on physics. The only thing that calculator can't account for is harmonics.


Originally Posted by SnakeWrangler
Originally Posted by TurkeyHunter
And make Kamila president

She’d just end up blowing it......
Re: POI of heavier vs. lighter bullets [Re: onlysmith&wesson] #8143664 01/26/21 03:31 AM
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Ballistic calculator has zero to do with the question asked.

The question asked was "I shot a bunch of bullets and set zero. Then I shot some other bullets (different weight/charge/velocity/etc) and they shot higher even though they were heavier. Why?"

The answer is two words: barrel harmonics

Re: POI of heavier vs. lighter bullets [Re: Big Fitz] #8143675 01/26/21 03:42 AM
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Originally Posted by Big Fitz
Heavier/slower bullet hitting higher than a lighter/faster bullet at 100 is barrel harmonics provided that everything else is the same.


^^^ this dude is brilliant!


Originally Posted by KRoyal
Sounds like a nice stick Fitz.

Originally Posted by Sailor
Fitz............. is right, ya know............
Re: POI of heavier vs. lighter bullets [Re: onlysmith&wesson] #8143676 01/26/21 03:42 AM
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roflmao

Re: POI of heavier vs. lighter bullets [Re: wp75169] #8143681 01/26/21 03:49 AM
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Originally Posted by wp75169
roflmao


cheers


Originally Posted by KRoyal
Sounds like a nice stick Fitz.

Originally Posted by Sailor
Fitz............. is right, ya know............
Re: POI of heavier vs. lighter bullets [Re: Big Fitz] #8143692 01/26/21 03:58 AM
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Originally Posted by Big Fitz
Originally Posted by wp75169
roflmao


cheers

happy3

Re: POI of heavier vs. lighter bullets [Re: onlysmith&wesson] #8143724 01/26/21 04:39 AM
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nidea

Over my head. When I try to think that hard it gives me a migraine.


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Re: POI of heavier vs. lighter bullets [Re: onlysmith&wesson] #8143764 01/26/21 06:28 AM
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I think it has more to do with harmonics than anything, comparing the POI of different loads at 100 yards. You can probably pick ten loads and shoot ten groups at a different point of impact with each load without adjusting the scope. Even with the exact same factory load, different lot of ammo, there is a good chance the new lot will have a different poi maybe by a lot or maybe by a little.

I have had two boxes of 170 grain corelokt 30-30 shoot two completely different poi by nearly 6” at 100 yards. I have experience the same thing with two different boxes of 80 grain Winchester PowerPoint .243 ammo.

Difference in POI with different loads has little if anything to do with velocity, weight, or BC inside 100 yards.

Last edited by Bryan C. Heimann; 01/26/21 06:29 AM.

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Re: POI of heavier vs. lighter bullets [Re: cowie14] #8143779 01/26/21 11:05 AM
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Originally Posted by patriot07
Ballistic calculator has zero to do with the question asked.

The question asked was "I shot a bunch of bullets and set zero. Then I shot some other bullets (different weight/charge/velocity/etc) and they shot higher even though they were heavier. Why?"

The answer is two words: barrel harmonics


I mean it's literally a question of trajectories, but okay.

Originally Posted by unclebubba
Hickshunter, you are plugging those numbers into an online calculator. That online calculator is asking about your zero distance, right? As you are changing velocity, but not changing your zero distance, the calculator is angling the barrel up to compensate for the difference in drop. That's why your numbers are wrong. Try the calculator with a zero distance of zero. Then you will see that the heavier bullet will drop faster and print lower based on physics. The only thing that calculator can't account for is harmonics.


Okay, this is actually a fair point. Unfortunately a zero distance of 0 yards wouldn't make any sense. The angles of the scope and the gun would have to be similar to a pizza slice. The trajectory at 25 yards has it rising 112 inches, lol.

The fact that the ballistic calculator is having to account for a slow bullet hitting higher at close ranges is really proof that velocity is causing OP's changes.


Originally Posted by cowie14
Positive compensation, that is the word you are looking for. Alex Wheeler knows more about it than anyone especially at 1k

http://www.geoffrey-kolbe.com/articles/rimfire_accuracy/tuning_a_barrel.htm

Here is an example at 600 yds:

42.4 2776fps
42.5 2786
42.8 2786
42.9 2805

not sure the group but maybe 1.25"

[im]https://texashuntingforum.com/forum/pics/userpics/2021/01/full-66266-277481-img_4970.jpg[/img]




This is really interesting, thanks for sharing. It does help explain why ladder testing is such a useful tool and how a rimfire barrel might be tuned for harmonics. Unfortunately, it just can't explain a 2" shift at 100 yards with accurate loads. A good shooting load that is tuned to your barrel's harmonics (minimal vertical dispersion) accounts for this, and thus any changes in POI are due to the trajectory of the bullets.

Last edited by HicksHunter; 01/26/21 11:05 AM.
Re: POI of heavier vs. lighter bullets [Re: onlysmith&wesson] #8143825 01/26/21 12:38 PM
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This is great information. I haven't spent a lot of time thinking it through at this level because I've never had to. I got lucky and found great ammo that has worked and bought it for years. I always got my own DOPE on paper at ranges out to 400. I haven't noticed lot to lot POI changes. Now that I may be looking for something different, I'm learning some new stuff.

We all know there's one hell of an explosion in the chamber and a huge pressure spike right there. It causes barrel movement. Call it harmonics (vibrations=movement) or very mild recoil. If this is to have an effect on POI, it has to occur before the bullet leaves the bore. It occurred on the first shot. I think if in my original post if I had stated "upward movement" instead of "recoil" there would be more agreement here. I'll drop the time in the barrel part of that theory. A different load and different weight of bullet would definitely create a different amount of pressure in the chamber, creating different movement-vibration-harmonics-mild recoil and effect POI.

I think the trajectory also comes into play, all things equal.

Now for the platform. Could all of this be exponential given that this is an AR (a good one) and my scope is way higher than most of our thinking on a typical discussion on this? Would there be more harmonic effect due to the way the barrel is supported in the action over a bolt rifle, and my scope height of about 2.550" have a greater effect on the trajectory over an average height of say 1.500".


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Re: POI of heavier vs. lighter bullets [Re: onlysmith&wesson] #8143848 01/26/21 01:04 PM
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Scope height, and barrel connected to action have nothing to do with this.

You build a leather whip 10' long and I build a leather whip 9' long. They will have different sine waves. That is rifle barrels.


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Re: POI of heavier vs. lighter bullets [Re: FiremanJG] #8143854 01/26/21 01:10 PM
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Originally Posted by FiremanJG
Scope height, and barrel connected to action have nothing to do with this.

You build a leather whip 10' long and I build a leather whip 9' long. They will have different sine waves. That is rifle barrels.

And this is not compounded by the action, it would be the same in a bolt action, all things equal?


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Re: POI of heavier vs. lighter bullets [Re: onlysmith&wesson] #8143857 01/26/21 01:15 PM
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For the sake of understanding let’s quit using the words “harmonics” and “sine wave”. Both are correct but for the sake of understanding let’s call it “barrel whip”. As in the movement a whip makes when you snap it.

Everyone may already be on the same page but I don’t think so.

Which way is the tail of the whip (barrel) pointed when the bullet exits, up or down?

Re: POI of heavier vs. lighter bullets [Re: FiremanJG] #8143860 01/26/21 01:17 PM
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Originally Posted by FiremanJG
Scope height, and barrel connected to action have nothing to do with this.

You build a leather whip 10' long and I build a leather whip 9' long. They will have different sine waves. That is rifle barrels.



Guess I should have read before I posted. You pretty much cover it here.

Re: POI of heavier vs. lighter bullets [Re: wp75169] #8143869 01/26/21 01:32 PM
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Originally Posted by wp75169
For the sake of understanding let’s quit using the words “harmonics” and “sine wave”. Both are correct but for the sake of understanding let’s call it “barrel whip”. As in the movement a whip makes when you snap it.

Everyone may already be on the same page but I don’t think so.

Which way is the tail of the whip (barrel) pointed when the bullet exits, up or down?


This makes about as much difference at close ranges as compensating for spin drift.

Re: POI of heavier vs. lighter bullets [Re: HicksHunter] #8143875 01/26/21 01:39 PM
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Originally Posted by HicksHunter
Originally Posted by wp75169
For the sake of understanding let’s quit using the words “harmonics” and “sine wave”. Both are correct but for the sake of understanding let’s call it “barrel whip”. As in the movement a whip makes when you snap it.

Everyone may already be on the same page but I don’t think so.

Which way is the tail of the whip (barrel) pointed when the bullet exits, up or down?


This makes about as much difference at close ranges as compensating for spin drift.


You can continue to argue with, well everyone else in this thread. And you will still be wrong.


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Re: POI of heavier vs. lighter bullets [Re: HicksHunter] #8143883 01/26/21 01:48 PM
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Originally Posted by HicksHunter
Originally Posted by wp75169
For the sake of understanding let’s quit using the words “harmonics” and “sine wave”. Both are correct but for the sake of understanding let’s call it “barrel whip”. As in the movement a whip makes when you snap it.

Everyone may already be on the same page but I don’t think so.

Which way is the tail of the whip (barrel) pointed when the bullet exits, up or down?


This makes about as much difference at close ranges as compensating for spin drift.



Then explain why we do load development instead of just loading everything to max? It’s not uncommon to have big groups in between two good ones. It’s suggested you will find two good nodes, one low and one high. They’re referring to powder charge and velocity, but often the faster load will print lower on the 100 yard target. Hmmm.... wonder if those two nodes are the top and bottom of the arc on the sine wave where the barrel is static for a moment before changing directions? I think JG covered that on the last page though.

I guess we have to agree to disagree.

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