pretty sure it works that way with all of them. Just guessing here but the more mass the finer the adjustment. Don't quote me on that though, I have just started to play with these things. Someone more knowledgeable like Cortina or Ezell might be able to confirm
Barrel tuners or other muzzle devices effect on velocity and velocity stats
- Thread starter darkangel_r2
- Start date
RegionRat
Gold $$ Contributor
Jim, yes more mass means you end up with smaller adjustments for some of the structural modes. However, the length of the barrel is one to one with respect to the OBT wave regardless of the mass. How effective the vibration tuners are, or what their mass ratio should be consumed a good chunk of my life.
If I showed the closed classical math for a simple 1.25” dia plain bbl section of a given steel with a given tuner mass on the end, it would start a flame war and make the no-maths puke.
All that math does is give a pretty fair estimate of the frequency of the structural modes. The amplitudes matter as much or more, but those are best measured in the lab than guessed-at with estimates of damping.
Designing tuners by predictive models wasn’t effective. It always boils down to lab work leads and analysis catches up. Spend enough money and they converge, but before that you usually cut to the chase and finish in the lab before the math models close and the budget is spent.
Many weapon systems went into full production before the math models caught up with the real world results.
So, in the real world, we have those equations but we still go apply strain gages and high frequency accelerometers and do what is called a modal survey to establish the important harmonics and mode shapes. Knowing those, we estimated the rough size of tuner mass to get control of the harmonics for a given ammunition and loading.
More recently, we take laser Doppler scans and it is much less work than pinging with modal hammers or gluing on sensors. None of which is cheap work or common outside of major labs. It just makes the task less labor intensive and a lot faster.
The design of tuned mass dampers isn’t new, but it is still often done faster by the seat of the pants by someone with lots of practical experience than it is with advanced math model predictions.
The basic view I will share is a simple one. For the wave propagation it is pure length. For the mode shapes it is driven by the square root of the stiffness divided by the mass.
So for a given barrel section and length, making frequencies shift in a significant way means trading off between large weights that move a little or small ones that move a lot, but any change in length takes the sound wave farther to reflect back.
Keep in mind, we are often jumping magnitudes between some of these modes, but if their waves line up to exit time, they tend to matter more. The shock wave is an example of a frequency so high that it goes back and forth along the bbl many times before the bullet reaches the muzzle.
Moving a donut along the bbl affects the whip harmonics more and leaves the sound wave propagation length the same, so there is some independant control of the OBT time and the structural harmonics.
Changing a typical muzzle tuner can cross couple both the sound waves and the harmonics because you are effectively changing the length of the OBT wave and structural harmonics at the same time.
The good news is having the threaded joints on the muzzle tends to help reduce the amplitude of the OBT wave. Those threads act like a crack in a tuning fork and reduce the efficiency of the ringing.
Damping was as important as the frequency tuning. It was the reason some of the old wooden stocks had upward pressure on the bbl, a similar effect to squelching a tuning fork with your finger tips. That doesn’t change the note, but it sure damps the hell out of the amplitude.
If I showed the closed classical math for a simple 1.25” dia plain bbl section of a given steel with a given tuner mass on the end, it would start a flame war and make the no-maths puke.
All that math does is give a pretty fair estimate of the frequency of the structural modes. The amplitudes matter as much or more, but those are best measured in the lab than guessed-at with estimates of damping.
Designing tuners by predictive models wasn’t effective. It always boils down to lab work leads and analysis catches up. Spend enough money and they converge, but before that you usually cut to the chase and finish in the lab before the math models close and the budget is spent.
Many weapon systems went into full production before the math models caught up with the real world results.
So, in the real world, we have those equations but we still go apply strain gages and high frequency accelerometers and do what is called a modal survey to establish the important harmonics and mode shapes. Knowing those, we estimated the rough size of tuner mass to get control of the harmonics for a given ammunition and loading.
More recently, we take laser Doppler scans and it is much less work than pinging with modal hammers or gluing on sensors. None of which is cheap work or common outside of major labs. It just makes the task less labor intensive and a lot faster.
The design of tuned mass dampers isn’t new, but it is still often done faster by the seat of the pants by someone with lots of practical experience than it is with advanced math model predictions.
The basic view I will share is a simple one. For the wave propagation it is pure length. For the mode shapes it is driven by the square root of the stiffness divided by the mass.
So for a given barrel section and length, making frequencies shift in a significant way means trading off between large weights that move a little or small ones that move a lot, but any change in length takes the sound wave farther to reflect back.
Keep in mind, we are often jumping magnitudes between some of these modes, but if their waves line up to exit time, they tend to matter more. The shock wave is an example of a frequency so high that it goes back and forth along the bbl many times before the bullet reaches the muzzle.
Moving a donut along the bbl affects the whip harmonics more and leaves the sound wave propagation length the same, so there is some independant control of the OBT time and the structural harmonics.
Changing a typical muzzle tuner can cross couple both the sound waves and the harmonics because you are effectively changing the length of the OBT wave and structural harmonics at the same time.
The good news is having the threaded joints on the muzzle tends to help reduce the amplitude of the OBT wave. Those threads act like a crack in a tuning fork and reduce the efficiency of the ringing.
Damping was as important as the frequency tuning. It was the reason some of the old wooden stocks had upward pressure on the bbl, a similar effect to squelching a tuning fork with your finger tips. That doesn’t change the note, but it sure damps the hell out of the amplitude.
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RegionRat
Gold $$ Contributor
We are often reminded of how lucky we were to run into certain people in our lives… I got to know some of the best folks in this community due to the working world topic, then got to start playing with matches after retirement.
In this household, we say a little prayer for Howard and Hughes Aircraft every time we have one of those moments…
In this household, we say a little prayer for Howard and Hughes Aircraft every time we have one of those moments…
dellet
Gold $$ Contributor
A good question always raises more questions.
I don’t have a clear answer of the original question, only more questions that would need to be answered before I could draw a conclusion.
I don’t think the actual original question can be answered with currently available technology. As far as I know, there is no way to measure actual muzzle velocity, without effecting what you are trying to test.
To a certain degree, a chronograph set yards away from the muzzle, measures the velocity of a bullet that is more or less stable. Lack of bullet stability robs velocity very quickly. So to accurately answer the question, you would need actual muzzle velocity, and down range velococity.
While a Magneto speed could come very close to true muzzle velocity, it will effect harmonics. That may clutter up down range statistics.
A muzzle brake diverts the gasses flowing from the barrel, both before and after bullet exit. One of the things this does is change where the bullet stabilizes in flight and more or less passes from sub sonic to super sonic flight. In some ways a bullet is not truly traveling at super sonic speeds until it out runs the gasses pushing past it when they exit the muzzle.
You would need to differentiate between any “push” that might accelerate the bullet without a brake, that would be lost with a muzzle brake.
From not so much a velocity gain using a brake, but less velocity loss due to a faster stabilization of the bullet. No turbulence from a tail wind of relatively heavier gasses.
Would any “push” lost causing a drop in velocity by adding a brake, be compensated for by a faster stabilization of the bullet, less velocity dropped over time to the chronograph?
Can that be measured and separated with current technology?
For a tuner to effect muzzle velocity, it would have to change either burn rate/efficiency or friction quality of the barrel. That is hard for me to understand how that would happen.
It would make more sense that dampening vibrations of the barrel, would allow a cleaner (for lack of better terms) release of the bullet from the muzzle.
Again a more stable flight, earlier in flight, could/should clean up numbers on the chronograph, if the technology is available to measure it accurately.
When we think chronograph, muzzle velocity is the first thought and that is basically internal ballistics. Time from ignition to bullet exit from the muzzle.
A tuner or brake will effect external ballistics, quality of flight. Time of flight to or across the measuring device. Taking that to the extreme, a chronograph has no idea if a bullet is flying true, or tumbling as it is read.
It seems the question would be,
“ Do muzzle devices effect the quality of flight?”
If so, How soon into flight, and how does that effect ES/SD numbers?
You likely will have two different answers, measuring velocity at two different distances.
Just a different perspective offered.
I don’t have a clear answer of the original question, only more questions that would need to be answered before I could draw a conclusion.
I don’t think the actual original question can be answered with currently available technology. As far as I know, there is no way to measure actual muzzle velocity, without effecting what you are trying to test.
To a certain degree, a chronograph set yards away from the muzzle, measures the velocity of a bullet that is more or less stable. Lack of bullet stability robs velocity very quickly. So to accurately answer the question, you would need actual muzzle velocity, and down range velococity.
While a Magneto speed could come very close to true muzzle velocity, it will effect harmonics. That may clutter up down range statistics.
A muzzle brake diverts the gasses flowing from the barrel, both before and after bullet exit. One of the things this does is change where the bullet stabilizes in flight and more or less passes from sub sonic to super sonic flight. In some ways a bullet is not truly traveling at super sonic speeds until it out runs the gasses pushing past it when they exit the muzzle.
You would need to differentiate between any “push” that might accelerate the bullet without a brake, that would be lost with a muzzle brake.
From not so much a velocity gain using a brake, but less velocity loss due to a faster stabilization of the bullet. No turbulence from a tail wind of relatively heavier gasses.
Would any “push” lost causing a drop in velocity by adding a brake, be compensated for by a faster stabilization of the bullet, less velocity dropped over time to the chronograph?
Can that be measured and separated with current technology?
For a tuner to effect muzzle velocity, it would have to change either burn rate/efficiency or friction quality of the barrel. That is hard for me to understand how that would happen.
It would make more sense that dampening vibrations of the barrel, would allow a cleaner (for lack of better terms) release of the bullet from the muzzle.
Again a more stable flight, earlier in flight, could/should clean up numbers on the chronograph, if the technology is available to measure it accurately.
When we think chronograph, muzzle velocity is the first thought and that is basically internal ballistics. Time from ignition to bullet exit from the muzzle.
A tuner or brake will effect external ballistics, quality of flight. Time of flight to or across the measuring device. Taking that to the extreme, a chronograph has no idea if a bullet is flying true, or tumbling as it is read.
It seems the question would be,
“ Do muzzle devices effect the quality of flight?”
If so, How soon into flight, and how does that effect ES/SD numbers?
You likely will have two different answers, measuring velocity at two different distances.
Just a different perspective offered.
In a world that successfully markets inline seating dies and portable mini arbor presses with load cells, I think the answer to the effects question is pretty straightforward to find. Do F-Class shooters put one on their barrels? I'm happy with that as the verdict of usefulness.
The rest of your questions cycle back to what exactly are we tuning when we tune? The short answer there is one of the following. I'm undecided if they are mutually exclusive.
- worthy of a lifetime of study and pursuit.
- not fully understood, but remarkably responsive to adjusting just one variable, the powder charge. (Do we need or want a second variable to hunt and chase?)
How does the bullet just leaving the chamber know there is or isn't a moveable weight screwed to the end of the barrel? There seems to just the one answer -- a resonant system of some kind -- and then down the rabbit hole you'll go.
As to MV variations, it might suit to start with looking at the muzzle energy difference implied by the MV ES or SD. Is it a big difference? Or just a bit of wobble in the bigger scheme? That might tell you where to start looking next.
Bill Norris
Back in the Day
So if this statement from (dellet) above is a fact then it seems to reason that it could change the M V E S & S D to some degree.
It would make more sense that dampening vibrations of the barrel, would allow a cleaner (for lack of better terms) release of the bullet from the muzzle.
It would make more sense that dampening vibrations of the barrel, would allow a cleaner (for lack of better terms) release of the bullet from the muzzle.
RegionRat
Gold $$ Contributor
@dellet with respect to what can or cannot be measured in ballistics research, yes we can start tracking bullets even before they leave the bore.
In fact, we can see their spin rates, precession, vibrations, etc. When we add how much easier it is to add high speed video, you would be shocked at what we can “see”.
Even short range ballistics labs have been using 35GHz to do short range study for a long time since they don’t have to be in the radar business but can just buy one commercially. I’ll check to see if there are examples in public domain and link them below.
@Bill Norris , yes, if the shock wave mode happens to be at the muzzle when the bullet exits, it can and does affect velocity stats as well as POI. That is true with or without bbl tuners. Why is debatable but cause effect is not news in this respect.
In fact, we can see their spin rates, precession, vibrations, etc. When we add how much easier it is to add high speed video, you would be shocked at what we can “see”.
Even short range ballistics labs have been using 35GHz to do short range study for a long time since they don’t have to be in the radar business but can just buy one commercially. I’ll check to see if there are examples in public domain and link them below.
@Bill Norris , yes, if the shock wave mode happens to be at the muzzle when the bullet exits, it can and does affect velocity stats as well as POI. That is true with or without bbl tuners. Why is debatable but cause effect is not news in this respect.
There is a tuner called the KSS ATS tuner that works the way you described.
It’s not a brake / tuner combo but the way it works is it uses existing muzzle threads and any brake with the appropriate threads can be fit in front of the tuner. The brake snugs up against and uses the tuner as a shoulder.
Yep that seems closer to what I want. I just don't want constriction forward of muzzle.
Hoot
Silver $$ Contributor
Though somewhat unrelated, I'd love to show up at an ARA rimfire match next season with that on my rig, just to see the looks I got! Extra ooh points if it can actually tune a rimfire bull barrel.
Hoot
Though somewhat unrelated, I'd love to show up at an ARA rimfire match next season with that on my rig, just to see the looks I got! Extra ooh points if it can actually tune a rimfire bull barrel.
Hoot
I like the ATS Tuners because you can use them with a suppressor or with a a thread protector for something that doesn’t allow suppressors or brakes
dellet
Gold $$ Contributor
As cameras have advanced I think a lot of theories hav changed, and some fairly wild ones have proven true.
Shooting suppressed raised a certain amount of questions in this area. Many people try to judge whether a bullet has gone super by whether or not they “heard the crack” vs checking actual speed.
The flip side of that is is shooting supers suppressed and realizing that it could be 8-10 yards before there is an audible crack.
High speed film of shock waves created by canalures or lube grooves.
While not someone deep in the ballistics world, he has some interesting related videos out. This one is shock waves.
I would be interested in information tracking bullets in the bore. How it’s done and what information is gathered.
I have always wondered what something like a standard M4 profile looked like. To a certain extent the bore would resemble the profile under pressure and the drastic changes in profile would create almost a hinge point for flexing with vibrations. That can’t be good for the bullet riding the bore.
Thanks for anything you can provide.
Calculating the natural frequencies of a barrel is not that bad. But how do you model how those modes evolve into actual barrel motion from shot start?
Is there are resolution difference between the two methods? Are you able to get the data along the whole length of the barrel at the same time or is it still single point as with a fixed sensor.
So speed of sound in the steel is driving the motion and the natural modes are the building response? That would explain modes 3-5 being more relevant as mode 6 is typically higher than the driving frequency and not really excited, 1&2 so low in frequency as to be a near constant over a typical load dev velocity spread. That leaves only 3-5 that change much durring the difference in MV a load dev setup might cover.
Isn't magnitude drastically reduced as you go up in mode number? Do these modes excite at the same time? If there is a difference is there a way to calculate the offset?
Like a deresonator? Place at antinodes to dampen muzzle movement?
How extreme do these mods need to be to become to counter the traveling sound wave? Does bead blasting do something, or do you need something aggressive like spiral fluting or the tacom treatment?
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The actual exit time shouldn't change really any but the frequency and amplitude of vibrations will change to put that previous exit time on the correct part of the waveform.
CharlieNC
Gold $$ Contributor
Correct. The phase shift is for the muzzle vibration and it is as important as the freq and amp for tuning.
RegionRat
Gold $$ Contributor
The exit time lines up with some harmonics, but the punch line was the very next one...
..."All that math does is give a pretty fair estimate of the frequency of the structural modes. The amplitudes matter as much or more, but those are best measured in the lab than guessed-at with estimates of damping."...
It was near impossible to parametrically estimate the amplitude with math models, but much easier to just get down into the tunnel and measure the magnitude and the effect.
With both methods, there were limits, but with the Laser Doppler, if you could get a line of sight to the surface, you could get data. Then, when fed into a high resolution model you could plot the frequency or time base and make amplified animations to help visualize the modes.
Once you have the characteristics of the system, you could tell which modes were constructive or destructive during the exit time.
They had lots of different names based on if they were just a mass or if they were considered TMDs or tuned mass dampers.
Almost any threaded joint tends to reduce OBT wave amplitude just because it looks like a "crack" in the structure and decreases the transmissibility. The speed of that sound wave over the length of the bbl is related to the material properties, but things that help are related to reducing the efficiency of the reflected wave to help reduce the amplitude.
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