Kmccord
Well-Known Member
IMR 7977 is the closest to H1000 according to Hodgdon webpage, finding that will be about as easy as finding H1000, hell throw a dart at any powder type and they are all hard to find.
Accurate Burn Rate chart that compares Hodgden-Alliant-Viht powders
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IMR 7977 is actually a lot faster than H1000 with a burn rate of 0,429
Here are some comparisons for H1000. All approximate a some chosen boundary conditions, and all relative but the best guess
at their relative relationships on burn rate. In my experience, I think N560 would be closest. Or Ramshot Magnum. Neither is
temperature insensitive, but N560 is an extruded powder and will act better than Ramshot which is a ball powder.
I know from my own experience, RL26 is not temperature insensitive. I don;t know about RL 25.
Here are some comparisons for H1000. All approximate a some chosen boundary conditions, and all relative but the best guess
at their relative relationships on burn rate. In my experience, I think N560 would be closest. Or Ramshot Magnum. Neither is
temperature insensitive, but N560 is an extruded powder and will act better than Ramshot which is a ball powder.
I know from my own experience, RL26 is not temperature insensitive. I don;t know about RL 25.
| RL25 | 0.384 | |
| N560 | 0.371 | |
| H1000 | 0.366 | |
| Ramshot Mag | | 0.345 |
| RL26 | 0.3397 | |
| Acc Magpro | | 0.3342 |
Here's a graph of velocity vs. charge weight for N565 in a 338 LM
Now using the actual velocities from chronograph and putting them in the QL model to back calculate burn rate one can look at burn rate over charge weight and pressure changes over time as charge weight goes up.
Here's the graph of burn rate vs. charge weight which in shape closely mirrors the velocity chart as expected.
What I like to do is then average the burn rates from these data, and use the new average as my "burn rate"
for my specific rifle and my specific bullet, and my specific cartridge. I use this new derived burn rate to then model
all my future loads with that same rig, and bullet weight, and cartridge. Its pretty accurate.
So, these graphs are from about a year ago. I certainly understand burn rate is not a constant. I understand well it varies with
many many things. But, I hope I know how to use the information I have to be a better reloader and shooter too.
In some of this work, it is also interesting that when I look for the velocity nodes and flat spots, and I graph MOA along with
velocity and burn rate, the lower MOA's often match the velocity node flat spots which the burn rate chart will mirror too.
Just interesting stuff. But this is why I like working with the numbers out of QL to rank my powders, and not the charts.
By the way, QL shows the burn rate of N565 is supposed to be .3109 in a .338 LM. My chart shows that in my rifle with
26 inch bbl. shooting 250 gr. bullets at these charge weights its actually .3506. So that demonstrates burn rate is not constant
and does vary by cartridge, by rifle, by charge weight/density of load, etc. Its all pressure, volume, temperature law related.
PVT analysis 101. But again, we need a starting point, a way to rank things as a start. Gotta make some comprimises somewhere just to get out of bed in the morning! Then you can get your nose in it and fine tune!
Now using the actual velocities from chronograph and putting them in the QL model to back calculate burn rate one can look at burn rate over charge weight and pressure changes over time as charge weight goes up.
Here's the graph of burn rate vs. charge weight which in shape closely mirrors the velocity chart as expected.
What I like to do is then average the burn rates from these data, and use the new average as my "burn rate"
for my specific rifle and my specific bullet, and my specific cartridge. I use this new derived burn rate to then model
all my future loads with that same rig, and bullet weight, and cartridge. Its pretty accurate.
So, these graphs are from about a year ago. I certainly understand burn rate is not a constant. I understand well it varies with
many many things. But, I hope I know how to use the information I have to be a better reloader and shooter too.
In some of this work, it is also interesting that when I look for the velocity nodes and flat spots, and I graph MOA along with
velocity and burn rate, the lower MOA's often match the velocity node flat spots which the burn rate chart will mirror too.
Just interesting stuff. But this is why I like working with the numbers out of QL to rank my powders, and not the charts.
By the way, QL shows the burn rate of N565 is supposed to be .3109 in a .338 LM. My chart shows that in my rifle with
26 inch bbl. shooting 250 gr. bullets at these charge weights its actually .3506. So that demonstrates burn rate is not constant
and does vary by cartridge, by rifle, by charge weight/density of load, etc. Its all pressure, volume, temperature law related.
PVT analysis 101. But again, we need a starting point, a way to rank things as a start. Gotta make some comprimises somewhere just to get out of bed in the morning! Then you can get your nose in it and fine tune!
Marine sniper
Well-Known Member
Veteran;
Your above chart shows a 60 FPS decrease in MV by adding .1 grain of powder? I have never seen an instance where adding powder resulted in losing MV, particularly .1 grain equaling 60 fps in a large case volume case.
Your above chart shows a 60 FPS decrease in MV by adding .1 grain of powder? I have never seen an instance where adding powder resulted in losing MV, particularly .1 grain equaling 60 fps in a large case volume case.
Boy oh Boy, you really know how to open a can of worms.........Ok, we will go there.
On one hand, it just begs the question why that spike up in velocity in the middle of the curve then the roller coaster down?
This load is N565 which is a very chunky extruded stick powder---I call the N 560 through N570 series of VV powders the chunky monkeys. They are very hard to measure accurately without weighing every charge, even then one can be off a little.
These curves were derived by averaging 4 shot groups. The paticular ES on these 4 shots was 26 with the high being 2950 and the low being 2924. The Standard deviation was 13.05. So it was not a stellar 4 shot group in terms of the quality of the ammo itself.
The ES on most other data points was in a range from 8 -14 with SD's ranging from 4-13. So it as a group was an outlier, indicating to me I could have gotten some bad charge weights in those 4 pieces of ammo. It also could reflect a very hot chamber that I did not allow to cool enough between shot strings thus affecting burn rate and velocities. Could be both.
Now, at a more fundamental level, you are really asking, why does a velocity curve flatten or even go DOWN with increasing charge weight? That seems to violate our simplistic view of the laws of physics doesn't it?
But, as it turns out, the scientific and physics reason why we see these flat spots in velocity and even a downward move in velocity
as we shoot higher charge weights is no mirage, and not solely related to as some will claim insufficient data to be statistically significant. I believe it is real. I have attached a chart I randomly pulled off the internet of velocity vs. charge weight. The flat spots and even some decline with increase in charge weight is shown. You can find thousands of samples like this from shooters right here on LRH or on the internet. It is real. It happens. Here is why.
Here is an excerpt from Chris Long's White Paper on Optimal Barrel Timing Theory which is very much based on barrel harmonics.
Chris is an electronics engineer who is very versed in physics and sin waves common to electronics engineering.
http://www.the-long-family.com/OBT_paper.htm
(This is not a secure sight but it works fine for me.)
The pressure pulse from the gasses in the chamber cause a traveling wave of stress that bounces back and forth along the barrel between receiver and muzzle, slightly changing the bore diameter in the process. Minimum dispersion of the shots will result when the rate of change of the bore diameter is at a minimum, and this dispersion will present the least sensitivity to load variations (charge, seating depth).
So, you have charge weights which fill a certain volume in the case, and are packed in a certain density in that case, and the powder you are using has a certain burn rate character which is also a function of volume, pressure, and density of packing, etc.
We cannot monitor chamber and barrel pressures along the length of the barrel dependent on how much of the powder is changed to gaseous state before exiting the barrel. That whole function depends on your bullet weight, your bullet seating depth, and the length of your particular barrel. But what we can monitor as a proxy for pressure is muzzle velocity. So, this is all related to barrel harmonics and optimum barrel time for your bullet and charge weight. In compressed charges, some powder may actually exit the barrel unburned, especially in a short barrel.
The barrel harmonics from differing charge weights and bullet seating depths result in the sine wave variations up and down the barrel which moves the point of impact of the bullet as the barrel flexes and rotates in different positions at barrel exit of the bullet.
As Long mentions, the barrel undergoes expansion and contraction in frequency cycles as the bullet moves down the barrel. The sonic and pressure waves move back and forth in the steel with pressure in the chamber exceeding 60,000 psig. Because the speed of sound in stainless steel is about 5000 m/s, these waves move back and forth through a well bedded barrel multiple times before the bullet exits.
This affects pressure all along the barrel, waves coming and waves going, and therefore it affects velocity based on whether the bullet encounters pressure waves coming back or leaving the barrel and so the timing and velocity of the bullet leaving the barrel is affected in counter intuitive ways.
Therefore a small change in a charge could produce a counter intuitive failure to increase or decrease the velocity if the difference in the charge caused the bullet move through regions or zones of conflicting pressure interference in the barrel.
Here is another white paper which may prove of interest on this subject.
https://www.frfrogspad.com/loaddev.htm
There are some outstanding references to barrel harmonics work which I have noted in past posts here on LRH which you can search for. The whole subject was barrel tuners and why they work. Videos and white papers.
One of the best is Varmintal.com a Lawrence Livermore retired physicist who has performed finite element modeling analysis on barrels in models. Very good pictures of barrel harmonics in the process. Amazing stuff. Wet noodles?
Varmint Al's Eclectic Web Pages
varmintal.com
Now, when you see a dramatic spike like the one you noted in my curve, its probably not all due to barrel harmonics and
may exaggerate the flattening and drop in velocity you will see by increasing charge weights in order to find the
"velocity nodes" where velocity flattens or even goes down some as charge weight goes up. It was more likely due to
bad charge measurement and or a hot chamber or both and some of the physics we discussed above.
One last thought. When you shoot a ladder test, you are looking for the spot where you get the least vertical dispersion in your shots on the target even though the charge weight goes up? Isn't that also counter intuitive in physics? I believe its the same reason you see flat spots or even decreases on the velocity graphs. Same phenomenon. Just different method to find the sweet spot where your loads will be most forgiving over a range of powder charge weights in your specific rifle, with your specific bullet,
for that specific powder. If you graph velocities from your ladder tests, I think you will see the same flat spots, not just smaller vertical strings on the targets themselves.
Now, aren't you glad you opened that can of worms?????
That's the answer to why the ladder test and the Satterlee tests work, and it explains as best I can why.
Now here's another LRH thread where this was similarly discussed and you will see some dissenting posters who don't believe this.
They say its not statistically valid. But you can make statistics say anything you want to. Statistically speaking on average every person in the world has one testicle and one breast, right??
HELP WITH SATERLEE VELOCITY TEST
No one said it burns inconsistent and then magically is consistent. But the same thing happens every time you run this test with any combo. You find spots where the velocity doesn't change even though the powder is increased. Sometimes for up to 1 grain of charge increase there is no velocity...
I started this link on page 7 top......but do read the whole thread. Its very valuable discussion on the whole.
Attachments
One other thought as the barrel harmonics cause sound and pressure waves to move back and forth in the barrel, the amount of friction the bullet experiences going down the barrel is also not a constant. So, small changes in bullet contact with the lands and rifling going down the barrel as it twists and turns due to harmonics may also be contributing factor to these flat spots in the velocity curve. A little more friction due to bullet resistance against an undulating barrel that is not perfectly straight for some milliseconds means less velocity at exit. All of these things play into counter intuitive physics results in the real world.
Here is an excellent source published in 1997 that essentially analyzes the Audette Ladder Test and says it works for the same reasons I explained above.
Man its all physics!
By the way, I believe the whole reason you will find a low node, and a high node or several nodes that work where the graph goes up and then flattens again is related to barrel harmonics and sin waves of pressure and sound in the steel barrel.
Different combinations of harmonics are produced with different charge weights, bullet seating, etc. So, you may find a higher velocity node where it all flattens or goes down because the harmonics happened to come back into play again just right.
So as in electrical harmonics, you may get a 2nd, 3rd, or 4th order harmonic sin wave at some different frequency as you go up the velocity curve and find another node. I believe its all related to unique system harmonics in your specific rifle with its specific barrel
taper and length, and weight, the powder burn rate, the volume of the cartridge, the bullet seating used, the weight of the bullet,
etc. Then its all vibration of that barrel as the sound and pressure waves move back and forth before the bullet exits.
Explanation of harmonics and orders of harmonics -- ie, sin waves
Man its all physics!
By the way, I believe the whole reason you will find a low node, and a high node or several nodes that work where the graph goes up and then flattens again is related to barrel harmonics and sin waves of pressure and sound in the steel barrel.
Different combinations of harmonics are produced with different charge weights, bullet seating, etc. So, you may find a higher velocity node where it all flattens or goes down because the harmonics happened to come back into play again just right.
So as in electrical harmonics, you may get a 2nd, 3rd, or 4th order harmonic sin wave at some different frequency as you go up the velocity curve and find another node. I believe its all related to unique system harmonics in your specific rifle with its specific barrel
taper and length, and weight, the powder burn rate, the volume of the cartridge, the bullet seating used, the weight of the bullet,
etc. Then its all vibration of that barrel as the sound and pressure waves move back and forth before the bullet exits.
Explanation of harmonics and orders of harmonics -- ie, sin waves
WildRose
Well-Known Member
To simplify... .Boy oh Boy, you really know how to open a can of worms.........Ok, we will go there.
On one hand, it just begs the question why that spike up in velocity in the middle of the curve then the roller coaster down?
This load is N565 which is a very chunky extruded stick powder---I call the N 560 through N570 series of VV powders the chunky monkeys. They are very hard to measure accurately without weighing every charge, even then one can be off a little.
These curves were derived by averaging 4 shot groups. The paticular ES on these 4 shots was 26 with the high being 2950 and the low being 2924. The Standard deviation was 13.05. So it was not a stellar 4 shot group in terms of the quality of the ammo itself.
The ES on most other data points was in a range from 8 -14 with SD's ranging from 4-13. So it as a group was an outlier, indicating to me I could have gotten some bad charge weights in those 4 pieces of ammo. It also could reflect a very hot chamber that I did not allow to cool enough between shot strings thus affecting burn rate and velocities. Could be both.
Now, at a more fundamental level, you are really asking, why does a velocity curve flatten or even go DOWN with increasing charge weight? That seems to violate our simplistic view of the laws of physics doesn't it?
But, as it turns out, the scientific and physics reason why we see these flat spots in velocity and even a downward move in velocity
as we shoot higher charge weights is no mirage, and not solely related to as some will claim insufficient data to be statistically significant. I believe it is real. I have attached a chart I randomly pulled off the internet of velocity vs. charge weight. The flat spots and even some decline with increase in charge weight is shown. You can find thousands of samples like this from shooters right here on LRH or on the internet. It is real. It happens. Here is why.
Here is an excerpt from Chris Long's White Paper on Optimal Barrel Timing Theory which is very much based on barrel harmonics.
Chris is an electronics engineer who is very versed in physics and sin waves common to electronics engineering.
http://www.the-long-family.com/OBT_paper.htm
(This is not a secure sight but it works fine for me.)
The pressure pulse from the gasses in the chamber cause a traveling wave of stress that bounces back and forth along the barrel between receiver and muzzle, slightly changing the bore diameter in the process. Minimum dispersion of the shots will result when the rate of change of the bore diameter is at a minimum, and this dispersion will present the least sensitivity to load variations (charge, seating depth).
So, you have charge weights which fill a certain volume in the case, and are packed in a certain density in that case, and the powder you are using has a certain burn rate character which is also a function of volume, pressure, and density of packing, etc.
We cannot monitor chamber and barrel pressures along the length of the barrel dependent on how much of the powder is changed to gaseous state before exiting the barrel. That whole function depends on your bullet weight, your bullet seating depth, and the length of your particular barrel. But what we can monitor as a proxy for pressure is muzzle velocity. So, this is all related to barrel harmonics and optimum barrel time for your bullet and charge weight. In compressed charges, some powder may actually exit the barrel unburned, especially in a short barrel.
The barrel harmonics from differing charge weights and bullet seating depths result in the sine wave variations up and down the barrel which moves the point of impact of the bullet as the barrel flexes and rotates in different positions at barrel exit of the bullet.
As Long mentions, the barrel undergoes expansion and contraction in frequency cycles as the bullet moves down the barrel. The sonic and pressure waves move back and forth in the steel with pressure in the chamber exceeding 60,000 psig. Because the speed of sound in stainless steel is about 5000 m/s, these waves move back and forth through a well bedded barrel multiple times before the bullet exits.
This affects pressure all along the barrel, waves coming and waves going, and therefore it affects velocity based on whether the bullet encounters pressure waves coming back or leaving the barrel and so the timing and velocity of the bullet leaving the barrel is affected in counter intuitive ways.
Therefore a small change in a charge could produce a counter intuitive failure to increase or decrease the velocity if the difference in the charge caused the bullet move through regions or zones of conflicting pressure interference in the barrel.
Here is another white paper which may prove of interest on this subject.
https://www.frfrogspad.com/loaddev.htm
There are some outstanding references to barrel harmonics work which I have noted in past posts here on LRH which you can search for. The whole subject was barrel tuners and why they work. Videos and white papers.
One of the best is Varmintal.com a Lawrence Livermore retired physicist who has performed finite element modeling analysis on barrels in models. Very good pictures of barrel harmonics in the process. Amazing stuff. Wet noodles?
Varmint Al's Eclectic Web Pages
varmintal.com
Now, when you see a dramatic spike like the one you noted in my curve, its probably not all due to barrel harmonics and
may exaggerate the flattening and drop in velocity you will see by increasing charge weights in order to find the
"velocity nodes" where velocity flattens or even goes down some as charge weight goes up. It was more likely due to
bad charge measurement and or a hot chamber or both and some of the physics we discussed above.
One last thought. When you shoot a ladder test, you are looking for the spot where you get the least vertical dispersion in your shots on the target even though the charge weight goes up? Isn't that also counter intuitive in physics? I believe its the same reason you see flat spots or even decreases on the velocity graphs. Same phenomenon. Just different method to find the sweet spot where your loads will be most forgiving over a range of powder charge weights in your specific rifle, with your specific bullet,
for that specific powder. If you graph velocities from your ladder tests, I think you will see the same flat spots, not just smaller vertical strings on the targets themselves.
Now, aren't you glad you opened that can of worms?????
That's the answer to why the ladder test and the Satterlee tests work, and it explains as best I can why.
Now here's another LRH thread where this was similarly discussed and you will see some dissenting posters who don't believe this.
They say its not statistically valid. But you can make statistics say anything you want to. Statistically speaking on average every person in the world has one testicle and one breast, right??
HELP WITH SATERLEE VELOCITY TEST
No one said it burns inconsistent and then magically is consistent. But the same thing happens every time you run this test with any combo. You find spots where the velocity doesn't change even though the powder is increased. Sometimes for up to 1 grain of charge increase there is no velocity...www.longrangehunting.com
I started this link on page 7 top......but do read the whole thread. Its very valuable discussion on the whole.
When you get to a certain volume of powder you start limiting the combustion rate especially with slower burning powders which is why we tend toward longer barrels with slower powders to get higher velocities.
Not only is there a point of diminishing returns as your charge increases, it can actually get to a point where it works against you by suppressing the burn rate.
Marine sniper
Well-Known Member
That was very thorough, thanks. I am going to read it again.
Peter Morton
Well-Known Member
Jeebers, Veteran. I didn't know there'd be homework!
Great information, though. I'm still digesting. And thank you!
Great information, though. I'm still digesting. And thank you!
