LOAD TESTING and BARREL TUNERS

[Steve Donlon]

Tim Sellars advocates that the function of the tuner ONLY affects the vertical distortion of barrel vibrational harmonics and re-aligns that vertical distortion with the bullet exit timing during "barrel whip" which in theory should cause group size to be smaller.

While on the subject of vibrations Tim has also indicated from his testing and findings there is a secondary high frequency vibration at the time of ignition that is created simply by the forces of the case body slamming against the chamber walls and the bolt lugs locking up. It travels along the barrel ahead of the harmonic vibrations and it will alter tuning. His theory indicates since there is only one spot in the complete powder charge testing that is affected by this high frequency vibration that increasing or decreasing the powder charge by 1/2 grain will move the tune away from this high frequency vibration and remove the affects of it on group size and tuner settings. He also goes on to say that the bullet can pick up this high frequency vibration and actually carry it along and produce instability. Evidence of this condition being present is seen while adjusting the tuner and actually not seeing any or much changes at all to the group size.

I believe Tim's reference here was after the primer strike but if you watch this video on "Believe the Target" with Erik Cortina Tim explains his theory there.

Looks like there are many ways to address the issue. From what I've seen with my rifles a heavy barrel and heavy muzzle brake help but the fine tuning is much more work if you want that 1" group @ 1000 yards

 

[Bill Norris]

Looks like there are many ways to address the issue. From what I've seen with my rifles a heavy barrel and heavy muzzle brake help but the fine tuning is much more work if you want that 1" group @ 1000 yards

yea, I agree it does take more testing/tuning efforts at longer distances. And for those such as Erik Cortina, an F-class Pro and tuner builder that actually does turn his tuner while shooting @ 1000 yds. I'm sure he finds that turning it during matches can help or hurt from the remarks I've heard him make. But, he was schooled by John Myers another huge winning F-class Pro and tuner builder that swore him to secrecy with the knowledge he shared with him. John also turned his tuner while shooting matches but with testing equipment there with him that he depended on for atmospheric data. From my experience I can honestly say conditions rule when it comes to tuning.

 

[CharlieNC]

Tim Sellars advocates that the function of the tuner ONLY affects the vertical distortion of barrel vibrational harmonics and re-aligns that vertical distortion with the bullet exit timing during "barrel whip" which in theory should cause group size to be smaller.

While on the subject of vibrations Tim has also indicated from his testing and findings there is a secondary high frequency vibration at the time of ignition that is created simply by the forces of the case body slamming against the chamber walls and the bolt lugs locking up. It travels along the barrel ahead of the harmonic vibrations and it will alter tuning. His theory indicates since there is only one spot in the complete powder charge testing that is affected by this high frequency vibration that increasing or decreasing the powder charge by 1/2 grain will move the tune away from this high frequency vibration and remove the affects of it on group size and tuner settings. He also goes on to say that the bullet can pick up this high frequency vibration and actually carry it along and produce instability. Evidence of this condition being present is seen while adjusting the tuner and actually not seeing any or much changes at all to the group size.

I believe Tim's reference here was after the primer strike but if you watch this video on "Believe the Target" with Erik Cortina Tim explains his theory

The rise and fall of the poi during ladder testing can be evaluated to show the muzzle vibration occurs due to energy movement which occurs at the speed of sound along the length of the barrel. Vaughn was the first to show this, and I used his technique to confirm the same for my load ladders. Long was on a similar wavelength with his obt theory. Besides being very fast the muzzle vibration amplitude is less than .005", so you can't see it.

 

[Leeinmichigan]

I can agree with everything said in the above posts based on the fact that an additional item (tuner) secured to the end of the barrel dampens harmonics. At short range, competitors need only adjust load to address condition changes.

 

[Steve Donlon]

The rise and fall of the poi during ladder testing can be evaluated to show the muzzle vibration occurs due to energy movement which occurs at the speed of sound along the length of the barrel. Vaughn was the first to show this, and I used his technique to confirm the same for my load ladders. Long was on a similar wavelength with his obt theory. Besides being very fast the muzzle vibration amplitude is less than .005", so you can't see it.

Don't those vibrations travel much faster? It seems if the bullet is going faster, then to effect the bullet they would have to go faster, much faster. What am I missing?

 

[CharlieNC]

Don't those vibrations travel much faster? It seems if the bullet is going faster, then to effect the bullet they would have to go faster, much faster. What am I missing?

Speed of sound in air is around 1100fps, but in steel around 16,000fps! Many cycles before the bullet accelerates from 0 to exit the muzzle.

 

[ELR LVR]

Speed of sound in air is around 1100fps, but in steel around 16,000fps! Many cycles before the bullet accelerates from 0 to exit the muzzle.

I was going to point this out, good call.
Speed of sound is different through different mediums and yes the fundamental barrel resonant frequency can transfer say 5 times back and forth before the bullet exits.
This does not take into account the upper harmonics
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Which is why there can be more than one Node
and the CORRECT....seating depth is highly important

 

[gunsandgunsmithing]

The rise and fall of the poi during ladder testing can be evaluated to show the muzzle vibration occurs due to energy movement which occurs at the speed of sound along the length of the barrel. Vaughn was the first to show this, and I used his technique to confirm the same for my load ladders. Long was on a similar wavelength with his obt theory. Besides being very fast the muzzle vibration amplitude is less than .005", so you can't see it.

Is that .005 from center or overall? It's more than that overall but bbl stiffness will dictate how much, of course. Easy to measure bbl stiffness without excitation but a function of Dan Lilja's barrel weight calculator also gives a stiffness number that is relative to deflection with a given amount of weight at the muzzle and different lengths/contours, etc. It's a great tool to play with....fwiw.

I will add...it has to be more than that in many cases simply due to potentially having near that much or more even without a tuner because of gravity. Gravity is already drooping the bbl even before excitation of any kind. And then we get into "equal and opposite and conservation of momentum. But none of that is necessary to USE a tuner....Which is what 99% of people here care anything about.

Benchrest Barrel Weight Calculation Program - Lilja

Download the program free. A problem frequently encountered by the benchrest gunsmith when building a new rifle or rebarreling a rifle is determining where to trim the new barrel blank to make the barrel and rifle the correct weight. Usually the other components of the rifle are weighed and the...

riflebarrels.com

 

[gunsandgunsmithing]

I can agree with everything said in the above posts based on the fact that an additional item (tuner) secured to the end of the barrel dampens harmonics. At short range, competitors need only adjust load to address condition changes.

Yes, that's one way. The two are very similar in the end goal. Of course that's to be shooting small but more specifically, it's about exit timing relative to muzzle position. But yessir! You can tune without a tuner and perfect tune is perfect tune. A tuner is a tool to KEEP ya in tune vs changing the load to get the same end result. In simplest terms, tuning either way is very much about timing.

 

[Rock Knocker]

Is that .005 from center or overall? It's more than that overall but bbl stiffness will dictate how much, of course. Easy to measure bbl stiffness without excitation but a function of Dan Lilja's barrel weight calculator also gives a stiffness number that is relative to deflection with a given amount of weight at the muzzle and different lengths/contours, etc. It's a great tool to play with....fwiw

Benchrest Barrel Weight Calculation Program - Lilja

Download the program free. A problem frequently encountered by the benchrest gunsmith when building a new rifle or rebarreling a rifle is determining where to trim the new barrel blank to make the barrel and rifle the correct weight. Usually the other components of the rifle are weighed and the...

riflebarrels.com

That was another question I had. My 260AI is a 30", one pro steered me towards 30", afterwards another said 28" were shooting better. Will tuners have a larger effect on longer or slimmer barrels?

 

[gunsandgunsmithing]

That was another question I had. My 260AI is a 30", one pro steered me towards 30", afterwards another said 28" were shooting better. Will tuners have a larger effect on longer or slimmer barrels?

You're catching on fast. This can get complicated but the important stuff is not rocket science, especially when it comes to making one work vs understanding every detail as to why.
Bottom line...yes, stiffness is a factor but to put it into perspective, the difference from extreme in tune to extreme out of tune on say, a 23" HV contour vs a 30" 1.250 straight is only about 1 mark. IOW and on MY tuner, that's about 4 marks vs 5 marks. So, percentage wise, it's significant but in use, that get lost in the noise as you are really only using an extreme out of tune group as a reference vs what I've ever seen related to condition changes with a given load. There's a lot in what I just said, to digest. So, just read it a time or two. I can see you are no dummy and that you have a good handle on this.

I will say this, because it's easy to fall into this trap...as I did for a while but vibration analysis proved me wrong. We are not altering the actual frequencie(s) but we are altering phase time. So, in a nutshell, a tuner moves an anti-node left or right to coincide with bullet exit. Really nothing but timing...afaik. So, yes, we can tune with a tuner by speeding or slowing the bbl....Or, we can speed or slow the bullet..Same thing, generally speaking and really not very general. Pretty specifically so. In fact, I've correlated one mark on my tuner as being about .3 of n133 in a ppc. Nope...I can not test and give that value for every possible combition of variables that come with things like cartridge, case capacity to bore ratio, powders, bullets and every possible load. So, it's certainly not an across the board answer. But the group shape progression can be correlated between tuner mark values relative to powder or seating depth changes. Yes, it can.

Keep in mind how little difference there is between significantly different bbl contours to help put this into a usable perspective.

 

[CharlieNC]

Is that .005 from center or overall? It's more than that overall but bbl stiffness will dictate how much, of course. Easy to measure bbl stiffness without excitation but a function of Dan Lilja's barrel weight calculator also gives a stiffness number that is relative to deflection with a given amount of weight at the muzzle and different lengths/contours, etc. It's a great tool to play with....fwiw.

I will add...it has to be more than that in many cases simply due to potentially having near that much or more even without a tuner because of gravity. Gravity is already drooping the bbl even before excitation of any kind. And then we get into "equal and opposite and conservation of momentum. But none of that is necessary to USE a tuner....Which is what 99% of people here care anything about.

Benchrest Barrel Weight Calculation Program - Lilja

Download the program free. A problem frequently encountered by the benchrest gunsmith when building a new rifle or rebarreling a rifle is determining where to trim the new barrel blank to make the barrel and rifle the correct weight. Usually the other components of the rifle are weighed and the...

riflebarrels.com

Mike I have observed amplitudes in the .002 to .005 range, for a total swing of twice that. These occur around the barrel exit time, before the major calculated frequencies kick in.

 

[gunsandgunsmithing]

Mike I have observed amplitudes in the .002 to .005 range, for a total swing of twice that. These occur around the barrel exit time, before the major calculated frequencies kick in.

I would agree with those numbers...yeah. Lots of weeds between here and there in terms of actually putting a tuner to use, though. In the end, most people don't care but I know you do. Thanks for your work!

I guess my point to detractors along these lines is simply that the bbl is in a state of deflection that shows up in amplitude...even before the trigger is pulled, due to gravity. And yes, speed of sound in the 416ss bbl. Yes, it gets pretty deep and I think, less than perfect...but in the end, most of those small factors get lost in the noise and just don't show up on the target and I'm talking zero's, not moa stuff...like high frequency vibrations that are just too far within other variables to be practical in use, with the wind blowing and the clock running. Frankly, even without those things..

 

[Rock Knocker]

You're catching on fast. This can get complicated but the important stuff is not rocket science, especially when it comes to making one work vs understanding every detail as to why.
Bottom line...yes, stiffness is a factor but to put it into perspective, the difference from extreme in tune to extreme out of tune on say, a 23" HV contour vs a 30" 1.250 straight is only about 1 mark. IOW and on MY tuner, that's about 4 marks vs 5 marks. So, percentage wise, it's significant but in use, that get lost in the noise as you are really only using an extreme out of tune group as a reference vs what I've ever seen related to condition changes with a given load. There's a lot in what I just said, to digest. So, just read it a time or two. I can see you are no dummy and that you have a good handle on this.

I will say this, because it's easy to fall into this trap...as I did for a while but vibration analysis proved me wrong. We are not altering the actual frequencie(s) but we are altering phase time. So, in a nutshell, a tuner moves an anti-node left or right to coincide with bullet exit. Really nothing but timing...afaik. So, yes, we can tune with a tuner by speeding or slowing the bbl....Or, we can speed or slow the bullet..Same thing, generally speaking and really not very general. Pretty specifically so. In fact, I've correlated one mark on my tuner as being about .3 of n133 in a ppc. Nope...I can not test and give that value for every possible combition of variables that come with things like cartridge, case capacity to bore ratio, powders, bullets and every possible load. So, it's certainly not an across the board answer. But the group shape progression can be correlated between tuner mark values relative to powder or seating depth changes. Yes, it can.

Keep in mind how little difference there is between significantly different bbl contours to help put this into a usable perspective.

Ive always had a fascination and good idea about the high speed vibrations that run up and down the barrel multiple times before bullet exit and trying to time bullet exit when the strongest part of the vibration is down near the chamber end. I think thats been my full understanding of "barrel whip".

I was always confused, even at the start of this thread, why vertical stringing was so prevalent and why vibrations are always running vertically. But now with the "garden hose" idea of the bullets effect by basically pushing on the barrel, or barrel sag from gravity, that could be the definition of "barrel whip" I have been missing and hence the prevalence of vertical stringing?

If my new understanding is correct; barrel whip is going to cause vertical stringing only(unless heat stress torques it left or right) but the vibrational harmonics can have a more random effect, if not timed correctly??? A thick barrel decreases whip and vibration but a long thin barrel will shoot just as well if timed perfectly?

 

[gunsandgunsmithing]

Ive always had a fascination and good idea about the high speed vibrations that run up and down the barrel multiple times before bullet exit and trying to time bullet exit when the strongest part of the vibration is down near the chamber end. I think thats been my full understanding of "barrel whip".

I was always confused, even at the start of this thread, why vertical stringing was so prevalent and why vibrations are always running vertically. But now with the "garden hose" idea of the bullets effect by basically pushing on the barrel, or barrel sag from gravity, that could be the definition of "barrel whip" I have been missing and hence the prevalence of vertical stringing?

If my new understanding is correct; barrel whip is going to cause vertical stringing only but the vibrational harmonics can have a more random effect, if not timed correctly??? A thick barrel decreases whip and vibration but a long thin barrel will shoot just as well if timed perfectly?

Ehhhh. It's not just vertical. People used to claim that but it's simply not true. I've done a couple of rounds of actual vibration analysis testing, fwiw. Even still, there are things that I can't say that I know for sure to be fact but I've seen a lot of things that I can say are fact and a few things that either I can't explain or that we simply didn't test for more specifically. It's great that you are interested in this. Frankly, I wish someone else would. I rely on engineers to interpret much of our testing and it'd be great to have an actual engineer do this very very specific testing further and with equipment that evolves seemingly every few months rather that years. The equipment to process data FAST enough is not cheap but not terrible either. And, tech is one thing that gets better and cheaper with time. I for one would welcome anyone with qualifications to do more testing. Jump right in but know that the why's are a far step from the how's, already. I hope the gains are big for the shooting community, but it gets tougher when the aggs are already as small as they are.

 

[CharlieNC]

Ive always had a fascination and good idea about the high speed vibrations that run up and down the barrel multiple times before bullet exit and trying to time bullet exit when the strongest part of the vibration is down near the chamber end. I think thats been my full understanding of "barrel whip".

I was always confused, even at the start of this thread, why vertical stringing was so prevalent and why vibrations are always running vertically. But now with the "garden hose" idea of the bullets effect by basically pushing on the barrel, or barrel sag from gravity, that could be the definition of "barrel whip" I have been missing and hence the prevalence of vertical stringing?

If my new understanding is correct; barrel whip is going to cause vertical stringing only(unless heat stress torques it left or right) but the vibrational harmonics can have a more random effect, if not timed correctly??? A thick barrel decreases whip and vibration but a long thin barrel will shoot just as well if timed perfectly?

I don't like the term "whip" because it greatly exaggerates the situation and distorts a proper understanding. As I mentioned the amplitude of muzzle vibration is only a few thou when the bullet exits whereas the "whip" that makes nice high speed video occurs later. Look at the amplitude of the poi during a ladder test and basic geometry translated over hundred(s) of yards back to the muzzle proves the point.

 

[Rock Knocker]

I don't like the term "whip" because it greatly exaggerates the situation and distorts a proper understanding. As I mentioned the amplitude of muzzle vibration is only a few thou when the bullet exits whereas the "whip" that makes nice high speed video occurs later. Look at the amplitude of the poi during a ladder test and basic geometry translated over hundred(s) of yards back to the muzzle proves the point.

Yeah, I dont think ive ever had the correct terms or definitions for what is what, but vibrations make sense to me and a different effect from the bullet moving down the barrel makes some sense to me. But i dont understand how "barrel whip" could really be a "vibration", or at least anything like the harmonic vibration traveling up and down the barrel.....

And gunsandgunsmithing, Im sort of surprised with tech now that rifle barrels havent had a laser like devise like the M1 Abrams tank. As far as I know there is a laser at the end of the muzzle pointing to a detector on the tank, if the muzzle deflects the laser deflects and a computer accounts for all of it. Maybe not having your rifle hooked to computer and electric aiming on the firing line but to study, I think that would give some answers.

 

[Steve Donlon]

Speed of sound in air is around 1100fps, but in steel around 16,000fps! Many cycles before the bullet accelerates from 0 to exit the muzzle.

Thanks, almost like electricity, traveling in different wave lengths, very fast but "electricity travels close to the speed of light" which is by far faster.

 

[jelenko]

Thanks, almost like electricity, very fast.

Well, electricity travels close to the speed of light which is just over 2,000,000,000 fps

 

[gpoldblue]

I can agree with everything said in the above posts based on the fact that an additional item (tuner) secured to the end of the barrel dampens harmonics. At short range, competitors need only adjust load to address condition changes.

All a tuner does is attenuate barrel vibration...that is to slow it down to varying degrees. A tuner will not/cannot speed up barrel vibrations. A tuner cannot compensate for downrange condititions...that why we shoot sighters and doping to compensate for conditions. Once the bullet leaves the crown,the tuner has done all it can do.....from there Mother Nature has the last say.