Seating Depth vs Tuner - what are your thoughts?

[Bronsin]

Alex, you should check touch point on my ppc barrel when you think of it one day. I would bet good money they aren't moving North of 50 thousanths in a season! I know that is likely the divide, and why different disciplines are drawing different conclusions.

My stuck jag FUPA from 2011-12 era was a perfect example "with the same barrel" to what you're saying on lengths. Seating is definitely more related to bullet/throat interface is what all my notes would indicate as well.

Tom

That would be an insane amount of throat erosion in the PPC. I don't have one single barrel in the last 4 years that has worn more than .005. Now the jam point? That's a different story.

 

[NC/Br Shooter]

What if:
Instead we think of it like adding a timing retardation device to an engine to keep it from knocking
it is not another variable, but a device to pull timing out of the engine
or
SHIFT its timing backward
A Tuner acts like this
View attachment 1723984

You must like em!!
Some do, some don't

 

[Bottom Fodder]

think of it most simply put
as timing an engine for optimal performance
it will not perform to its optimum without being timed correctly
your question is akin to asking
what is timing an engine? and what is the science behind it?
which is a good question to understand what one is actually doing, which with a timing light would be
Simply = timing the spark relative to Top Dead Center of the Pistons Travel.
----
when we time bullet exit timing, by using seating depth, we have to understand that a bullet spends
time, it does not instantly Teleport itself to our intended target
time for spark to happen, ignition to happen, flame front to happen (see a similarity with an engine?)
So Time, traveling in the bore,
T=D/S (Time = Distance/Speed
30 inch bore = 2.5 ft
lets use 3000 fps for velocity
the Time a bullet spends in the bore before exit is
2.5/3000 = .0008333 seconds
(As a side note trivia special this is also why it is jokingly said a barrel wears out in approx 1.6 seconds which is equivalent to approx 2000 rounds spending 800 microseconds each in a bore.)
----
within this amount of .000833 second time there are 2 major harmonics happening with the barrel
a low Freq Harmonic which is the loaded harmonic under powder igntion which I have seen to be approx
108 hz
the higher Freq Unloaded Harmonic which is the natural resonant freq of the fat thick barrel steel which we can for the most part ignore since that high of a freq will be a very low amplitude freq
the Low Freq will always be of higher amplitude (more peak to peak swing)
Same as a guitar string, the big heavy fat E string you can see actually vibrate
The higher Freq E String you really cannot due to the lower amplitude
this Lower Freq. but one of Higher Amplitude, is the major component we are tuning our bullet exit to... since this is the main freq we see the largest up and down swing of
(I would like to also complicate things by adding here, that the speed of sound in SS is approx 19,000 fps
Which means...these vibrational frequencies can travel back and forth rebounding from one end of the barrel to the other around 5 times before the bullet even exits, and collide and create standing waves and complicate matters further which we cannot calculate when or where they will happen,
A Standing Wave in Radio Coms is one reason we do not use a Full Wave Antenna.
so is another importance for finding a Node in a rifle barrel
Imagine a sudden collide causing catostrophic resonance at the end of the barrel the instant the bullet is exiting, I can imagine thats why we can actually tune a 6 PPC to shoot really bad if we try lol.
Or why some factory ammo shoots really badly but handloads may print 1/4 MOA.
you can watch vids on you tube of what is called "barrel whip"
I can find one for you if you want but a 50 BMG barrel will look like a wet noodle under loaded recoil
BEFORE the bullets exits the muzzle
----
You want to time your bullet exit, like timing an engines optimum spark ignition, to the optimum swing of the barrel
or where the barrel is at the same spot every time in its swing
this could be during its up peak, its down peak, or at a node (Dead Spot)
since like a piston, there is what is called "Dwell Time" when it reaches it upmost or downmost travel and has to overcome momentum to reverse direction again which also adds time to this dwell before reversion.
Now keep in mind a barrel does not just swing up and down only but vibrates more in an oval pattern
Since, there is not only a vertical component but also a horizontal componant to its vibration.
You combine a Horizontal in the X axis with a Vertical in the Y Axis ...and you get an oval.
the more oval or round this vibrational pattern, the less dwell time at peaks
Which is one reason why every barrel is said to behave differently due to internal stresses which cause each barrel to behave differently as well as it own profile
---
If you had a barrel which vibrated in a circular pattern you could not time the bullets exit to a peak and then would have to time to a Node, or dead spot
Harmonics play the effect on how and when a Node pops up
harmonics are multiples of the fundamnetal frequency
we have the 3rd, 5th, 7th etc harmonics in music for example
the higher up we go in Freq, the lower the amplitude in the harmonic
a 3rd harmonic is 3x times the fundamental freq. for instance.the 5th, is 5 times etc.
so every half cycle or peak of the 3rd when directly 180 degrees out of phase with the original fundamental freq = will completely cancel out each other, or attenuate causing a node
the same as noise cancellation.
However, the Opposite or Accentuating also happens when both are in phase, which causes a much higher amplitude, kind of like when the Sun and the moon are aligned or in phase with high tide causing an even higher tide called Spring Tide.
So you do NOT want your bullet to exit during that event.
---
Therefore since most of us do not have the equipment to measure what our barrels vibrating frequency is
Nor have the ability to measure the amplitude of the Harmonics to determine how much attenuation we will get at each Node...
...we simply start at a known constant for seating depth which is usually
Touching the lands and working backward
Or Jammed into the Lands and working backward until we see our group pattern suddenly close up and shrink
---
This is the science of using seating depth to time bullet exit and what we are timing that bullet exit to.
Also, since this optimum event can happen more than once during a bullets travel, we can have more than just one seating depth possible, meaning this event can happen at every .040" or every .060" space apart of seating depth.
Some seating Depths, can have more Attenuating Harmonics present causing a very forgiving Node...
...so will provide for a Verrrry wide forgiving window of seating depth, this is what I look for in my optimum seating depth.
lets say you see no difference in POI or group size for .020" difference in seating depth
then place your bullet in the middle of that to account for bullet length variations and you will have a very forgiving window.

Wow good example OK I’ve probably timed way more engines than I’m am years old. And I understand that fully( advice/ retard) But does seating depth change the time it takes the bullet to exit the barrel to optimize or does it change the harmonics of the barrel to optimize or both

 

[ELR LVR]

Wow good example OK I’ve probably timed way more engines than I’m am years old. And I understand that fully( advice/ retard) But does seating depth change the time it takes the bullet to exit the barrel to optimize or does it change the harmonics of the barrel to optimize or both

just changes the exit timing,
to be at the optimum time of the barrels position
relative to where you are aiming it
---
to change the time it takes to exit the barrel, as in changing the time it spends traveling down the barrel and getting it to come out sooner
---Would be load change, or velocity change, which is another way also
So we can speed up the bullet or slow it down to change when it exits
or simply change the forward or backward position the bullets starts from
That's the whole essence of load devlopment
but most of us want to hit a target velocity
then alter seating depth to fine tune the accuracy of the load in
I find seating depth to be the prime factor of "fine" tuning the load

IE: you want the barrel to be pointing at the same spot you are aiming
---
and if you ever watched a vid of barrel whip, it is so pronounced it is easily visible
not to mention it is sometimes visible in slow motion to see the whole length of the barrel moving in a wavelike pattern not simply the muzzle swinging up and down
---
So considering .001" of barrel movement is roughly .100" POA change at the target at 100 yds
you can see why we need our bullet to exit at the optimum time

 

[Longrange57]

The nice thing about hobbies is that we get to do them the way we want. Having said that, a friend who shoots competitively in short range group did a little test a while back. He shot the same load (with a tuner that was not adjusted between tests) at 60 degrees and later at 80 degrees. The groups were the same. We have a lot of what you could describe as ideal load testing conditions around here and he has the use of a well built 200 yard range with a couple of excellent concrete benches that are covered. They are about 15 minutes from his house. He likes to test, and is an excellent shooter. Both of us think that the width of his node is attributable to the tuner, and that it is an advantage. Certainly matches are won without tuners, but neither of use can find a reason not to avail ourselves of that kind of advantage.

Boyd, thanks for the feedback. We have about 2.5 years of research now showing pressure spikes to be the culprit and causes harmonic changes shot to shot. We have phenomenal fast acting pressure transducers today that were not around years ago. We all know CUP is very different from actual PSI. When considering these spikes, the manufacturers are full aware of them. Mike said the key word in a previous post about variables. We have about 12 distinct events taking place from firing pin release to bullet exit that all play a part in the harmonic event. Some testing in the past was performed by dry firing without a round and the harmonics are different each time. One of the big issues, once again is having 5 exact loads, with the powder having the exact square inch area. This is next to impossible, although one individual years ago actually had a manufacturer (Euro Chemie) cut the extrusions to a very high tolerance and then literally counted the kernels. He saw a difference. Variances in square area can change the burn rate. With compressed loads and certain powders, spikes can be all over the place.
NDA's are in place, patents are being prepared, and the group doing more research doesn't want certain information released yet. Everyone here has presented some very good info and this project if taken on by a manufacturer will be years in the workings. It will change nothing we do. Load development with or without a tuner will still be necessary. Shooting organizations will not approve a regulation device until a manufacturer has it in circulation for a while. Regulating the pressure spikes will simply regulate the harmonics a bit better shot to shot. We have seen the evidence with one caliber and doing research on 2 others currently. It appears that with or without a tuner, group size can become smaller by controlling pressure spikes. We might think we don't have spikes, but in reality, we do. My hat is off to those who shoot small whether a tuner is involved or not. Lots of heads are better than one. I've gleaned much good information from this forum through the years. Thanks for all you do Boyd.

 

[gunsandgunsmithing]

just changes the exit timing,
to be at the optimum time of the barrels position
relative to where you are aiming it
---
to change the time it takes to exit the barrel, as in changing the time it spends traveling down the barrel and getting it to come out sooner
---Would be load change, or velocity change, which is another way also
So we can speed up the bullet or slow it down to change when it exits
or simply change the forward or backward position the bullets starts from
That's the whole essence of load devlopment
but most of us want to hit a target velocity
then alter seating depth to fine tune the accuracy of the load in
I find seating depth to be the prime factor of "fine" tuning the load

IE: you want the barrel to be pointing at the same spot you are aiming
---
and if you ever watched a vid of barrel whip, it is so pronounced it is easily visible
not to mention it is sometimes visible in slow motion to see the whole length of the barrel moving in a wavelike pattern not simply the muzzle swinging up and down
---
So considering .001" of barrel movement is roughly .100" POA change at the target at 100 yds
you can see why we need our bullet to exit at the optimum time

I would say seating depth changes exit time mostly by changing the pressure curve, how the pressure builds, mostly. There may be something to harmonics too when the bullets impacts the lands. Particularly with largish jumps. Just a swag though.

 

[JFrank]

Seating is definitely more related to bullet/throat interface is what all my notes would indicate as well.

I think the bullet / throat interface relationship changes the chamber pressure as the throat wears.
~ I was typing this as Mike posted above, I’m not describing as well as others either. My apologies

 

[Bottom Fodder]

Ok let me answer my own question in simple form and you tell if Im right or wrong.
Just for illustration Using “touch” as “0” If I jump the bullet 10 thousand then theoretically the bullet has to travel 10 thousands further to exit. Were as if you jammed the bullet say 10 thousand the time would be shorten. the barrel which due to the harmonics of the barrel would change where in the wave the bullet would exit. And in trying to find the “sweet spot” you’re actually changing the time it takes the bullet to exit the barrel.

Tunner
Works by changing the harmonics of the barrel and in doing so your able to get the bullet to exit the barrel when it’s at its “sweet spot”
Am I close to how this all works

 

[Bill Norris]

Ok let me answer my own question in simple form and you tell if Im right or wrong.
Just for illustration Using “touch” as “0” If I jump the bullet 10 thousand then theoretically the bullet has to travel 10 thousands further to exit. Were as if you jammed the bullet say 10 thousand the time would be shorten. the barrel which due to the harmonics of the barrel would change where in the wave the bullet would exit. And in trying to find the “sweet spot” you’re actually changing the time it takes the bullet to exit the barrel.

Tunner
Works by changing the harmonics of the barrel and in doing so your able to get the bullet to exit the barrel when it’s at its “sweet spot”
Am I close to how this all works

I Believe you are. The tuner is aligning barrel whip with exit time.

 

[CharlieNC]

Limited experience on my fclass rifle.... seating depth optimization had a tremendous impact on accuracy. Tuner adjustment had minimal effect and don't see how it could replace seating depth, but looks to maintain tune across major temperature swings during the year.

 

[Bottom Fodder]

I Believe you are. The tuner is aligning barrel whip with exit time.

Thank you Bill, So a simple question CAN be answered with a simple answer

 

[ELR LVR]

Ok let me answer my own question in simple form and you tell if Im right or wrong.
Just for illustration Using “touch” as “0” If I jump the bullet 10 thousand then theoretically the bullet has to travel 10 thousands further to exit. Were as if you jammed the bullet say 10 thousand the time would be shorten. the barrel which due to the harmonics of the barrel would change where in the wave the bullet would exit. And in trying to find the “sweet spot” you’re actually changing the time it takes the bullet to exit the barrel.

Tunner
Works by changing the harmonics of the barrel and in doing so your able to get the bullet to exit the barrel when it’s at its “sweet spot”
Am I close to how this all works

Yes on the first one, you're altering the starting point of the bullet
there are other factor that contribute though with jump vs jam
The more jump (longer the Throat) the more the bullet gets to accelerate before hitting the rifling and theoretically you bump up velocity, insert Weatherby's theory with long throats.
So there is some pressure dynamics involved, but I do not think nor see the pressure or velocity change much with say only a .005" change in seating depth, but I DO SEE a very noticeable difference in group size when close to optimum exit time, vs just barely outside of it
So I suggest the seat depth contributes mostly to bullet exit time.
---
the second as to the tuner
Let me explain it another way as far as Phase Shift in the cycle
According to what I understand and again the better tuner experts may elaborate but,
Think of it like your wives Period
Lets say she has her period on the 30th of every month
and The doctor gives her a pill that suddenly causes her to have her period on the 5th of the month now
it is still the same amount of time happening in between each cycle.
She did not change the frequency of her period, not did she change the duration of her period
she only changed the cycle "Timing" forward or backward in the time of the month in which it happens
Phase Shift is changing the cycle event forward or backward
Which is what I understand a tuner to do.
The frequency stays the same, but changes when the time of when the cycle of peak to peak happens.
So lets say your bullet exits during an upswing in the cycle toward full amplitude.
and you turn your tuner out, and it changes the full cycle more forward so that now the peak, or full upswing happens the moment your bullet exits. the full downward or full upward stop point is the same as a person swinging on a swingset where during the upswing, the person has to stop before going back down
you want your bullet exiting at that stop of one of those peaks of a cycle.
a FULL cycle consisting of --- one full upswing and one full downswing.
Think of a sine wave, changing the phase is merely changing when the start and stop of a cycle happens
it does not change its frequency
so you may pick either peak, the up or the down, but one may be a better tune than the other.
You can accomplish the same thing with bullet seating depth and exit timing, but not after the bullet is seated,
Whereas with the tuner, you CAN change, when the peak happens --- at the time the bullet exits,
Notice pic on the right,
the red and blue full cycle are the same frequency since they have the same distance from peak to peak
but the blue one happens later in time, than the red
the blue waveforms cycle, or phase, has been shifted forward or later in time
Just like your wives CYCLE of her period has been shifted forward in time with a pill
Now we get into some Trig and Geometry which I dont know if you are into
but - the Theta Sign at the bottom, represents the Phase shift, in degrees of cycle event
there are 360 degrees in a cycle
at 0 you have zero value, at 90 degrees you have full peak value or amplitude
and The Trig and geometry correlate with Pythagorean Theorum at whatever degree in between you measure the amplitude of the cycle
at 45 degrees for example the ratio of the full value is the Cosine of the Angle of 45 Deg which is .707
---
So similarly is how we measure our wall voltage, at 120 volts since it is taken at 45 degrees of the cycle and the ratio of a full value peak of 170 volts x .707 is 120 volts
Which you may have commonly heard the term as RMS value, short for "Root Means Squared"
---
Similarly also, wind when coming from 45 degrees to the shooter is measured in the same manner using the cosine of the angle ----- as a ratio of the full value
Sorry if this suddenly got confusing but just throwing other analogies out there you may know to help relate Cycles and phase
----
So when we Turn our Tuner, we are changing "The Phase" by a certain amount of degrees forward or backward in the cycle of a barrels vibrational frequency, or IE: imparting a "Phase Shift"

 

[Bill Norris]

Thank you Bill, So a simple question CAN be answered with a simple answer

Yea a very simple answer. All of the complicated stuff is happening beyond the wording.

 

[Bottom Fodder]

Yes on the first one, you're altering the starting point of the bullet
there are other factor that contribute though with jump vs jam
The more jump (longer the Throat) the more the bullet gets to accelerate before hitting the rifling and theoretically you bump up velocity, insert Weatherby's theory with long throats.
So there is some pressure dynamics involved, but I do not think nor see the pressure or velocity change much with say only a .005" change in seating depth, but I DO SEE a very noticeable difference in group size when close to optimum exit time, vs just barely outside of it
So I suggest the seat depth contributes mostly to bullet exit time.
---
the second as to the tuner
Let me explain it another way as far as Phase Shift in the cycle
According to what I understand and again the better tuner experts may elaborate but,
Think of it like your wives Period
Lets say she has her period on the 30th of every month
and The doctor gives her a pill that suddenly causes her to have her period on the 5th of the month now
it is still the same amount of time happening in between each cycle.
She did not change the frequency of her period, not did she change the duration of her period
she only changed the cycle "Timing" forward or backward in the time of the month in which it happens
Phase Shift is changing the cycle event forward or backward
Which is what I understand a tuner to do.
The frequency stays the same, but changes when the time of when the cycle of peak to peak happens.
So lets say your bullet exits during an upswing in the cycle toward full amplitude.
and you turn your tuner out, and it changes the full cycle more forward so that now the peak, or full upswing happens the moment your bullet exits. the full downward or full upward stop point is the same as a person swinging on a swingset where during the upswing, the person has to stop before going back down
you want your bullet exiting at that stop of one of those peaks of a cycle.
a FULL cycle consisting of --- one full upswing and one full downswing.
Think of a sine wave, changing the phase is merely changing when the start and stop of a cycle happens
it does not change its frequency
so you may pick either peak, the up or the down, but one may be a better tune than the other.
You can accomplish the same thing with bullet seating depth and exit timing, but not after the bullet is seated,
Whereas with the tuner, you CAN change, when the peak happens --- at the time the bullet exits,
Notice pic on the right,
the red and blue full cycle are the same frequency since they have the same distance from peak to peak
but the blue one happens later in time, than the red
the blue waveforms cycle, or phase, has been shifted forward or later in time
Just like your wives CYCLE of her period has been shifted forward in time with a pill
Now we get into some Trig and Geometry which I dont know if you are into
but - the Theta Sign at the bottom, represents the Phase shift, in degrees of cycle event
there are 360 degrees in a cycle
at 0 you have zero value, at 90 degrees you have full peak value or amplitude
and The Trig and geometry correlate with Pythagorean Theorum at whatever degree in between you measure the amplitude of the cycle
at 45 degrees for example the ratio of the full value is the Cosine of the Angle of 45 Deg which is .707
---
So similarly is how we measure our wall voltage, at 120 volts since it is taken at 45 degrees of the cycle and the ratio of a full value peak of 170 volts x .707 is 120 volts
Which you may have commonly heard the term as RMS value, short for "Root Means Squared"
---
Similarly also, wind when coming from 45 degrees to the shooter is measured in the same manner using the cosine of the angle ----- as a ratio of the full value
Sorry if this suddenly got confusing but just throwing other analogies out there you may know to help relate Cycles and phase
----
So when we Turn our Tuner, we are changing "The Phase" by a certain amount of degrees forward or backward in the cycle of a barrels vibrational frequency, or IE: imparting a "Phase Shift"
View attachment 1724088

Thanks I will just stay with using a time light and seating depth to advance and retard instead of a tunner and leave the math behide the Science to others
Thanks again

 

[swd]

Thanks I will just stay with using a time light and seating depth to advance and retard instead of a tunner and leave the math behide the Science to others
Thanks again

If you can open a bottle with a twist top you can work a tuner.. The numbers on it are only for reference.

 

[BoydAllen]

Boyd, thanks for the feedback. We have about 2.5 years of research now showing pressure spikes to be the culprit and causes harmonic changes shot to shot. We have phenomenal fast acting pressure transducers today that were not around years ago. We all know CUP is very different from actual PSI. When considering these spikes, the manufacturers are full aware of them. Mike said the key word in a previous post about variables. We have about 12 distinct events taking place from firing pin release to bullet exit that all play a part in the harmonic event. Some testing in the past was performed by dry firing without a round and the harmonics are different each time. One of the big issues, once again is having 5 exact loads, with the powder having the exact square inch area. This is next to impossible, although one individual years ago actually had a manufacturer (Euro Chemie) cut the extrusions to a very high tolerance and then literally counted the kernels. He saw a difference. Variances in square area can change the burn rate. With compressed loads and certain powders, spikes can be all over the place.
NDA's are in place, patents are being prepared, and the group doing more research doesn't want certain information released yet. Everyone here has presented some very good info and this project if taken on by a manufacturer will be years in the workings. It will change nothing we do. Load development with or without a tuner will still be necessary. Shooting organizations will not approve a regulation device until a manufacturer has it in circulation for a while. Regulating the pressure spikes will simply regulate the harmonics a bit better shot to shot. We have seen the evidence with one caliber and doing research on 2 others currently. It appears that with or without a tuner, group size can become smaller by controlling pressure spikes. We might think we don't have spikes, but in reality, we do. My hat is off to those who shoot small whether a tuner is involved or not. Lots of heads are better than one. I've gleaned much good information from this forum through the years. Thanks for all you do Boyd.

Big smile, yer welcome

 

[ELR LVR]

You must like em!!
Some do, some don't

I like advancements in technology that help with accuracy and skill with marksmanship
any advancement that does this is worthy of consideration as well as the engineers who design such devices and instruments
I mean, we could use the same logic regarding 5 inch wide forearms stocks
which I personally think take a lot of realistic skill level out of shooting so I dont even own one
so in one aspect using that logic I could agree with how you are thinking
but I believe a Tuner is a sound device that is a personal choice just like what power scope you may choose to use for competition
you can use an 80x power to see bullet holes at 1000
or stay with using the minimum you can see your target with such as open sights at 600 etc.
Its just another advanced level of gear that helps, if you choose to use one.
and within this line of thinking, the serious High Level Top Competitors are likely going to stack every card in the deck in their favor, such as having a tuner on, regardless of if they actually turn it during a match or not
having the option there, is whats important sometimes to winning 1st place vs merely competing for fun.
Kinda like a divining rod
One does not have to understand "How" it works, to know that they work.
---
The first time I was told about "Witching sticks" I thought I had been picked as the target of being joked with at the family gathering that weekend, Until I was handed and held 2 "L" shaped pieces of coat hanger in my hands and told to walk out across the property without thinking of anything
and located the underground water pipe for the property not knowing what I had even done.
And the rods kept crossing very time a walked across the underground pipe.
I still did not believe what was happing was actually happening. Yet I could not deny it in front of my face.
Similarly, A year ago I thought Tuners were a bunch of phooey just to make up for piss poor load development
but now that I understand them better I realize I was being just as skeptical for simply not understanding that which I did not know.

 

[tom]

That would be an insane amount of throat erosion in the PPC. I don't have one single barrel in the last 4 years that has worn more than .005. Now the jam point? That's a different story.

That's what I was saying/betting, as even our BRA's aren't terrible. My last 2 wsm's moved a little over 50 thou in a season. I learned, from testing early on, to measure and follow after each time I cleaned them. It worked quite well for me, until the Saturday it measured shorter a thou, but it got 19/20ths through the best aggs I've put together! Lol

Tom

 

[Bottom Fodder]

If you can open a bottle with a twist top you can work a tuner.. The numbers on it are only for reference.

Probably so but not my cup of tea