Seating Depth vs Tuner - what are your thoughts?

[Shooter13]

I dont use a tuner.. i really think people try to skip seating depth because cortina said something like that in a pod cast.. cortina is awsome.

I don't think any serious BR shooter skips anything, I do the powder test, I do the seating test, I do the neck tension test, I do the crush test, I do the ................. AND THEN I WORK ON THE TUNER and regularly get my butt handed to me in a paper bag, no roses, no flowers and no money. Oh, no fake wood.
A couple of years ago I was shooting a 30BR, no one had ever shot a perfect score with a 30 (264). Mike Schubert and I were neck & neck until the last target, I missed one and Mike hit the all, cost Danny Hensley $100 (he promised the first person to shoot a perfect score would receive the $100). I'm sure that pressure is what got me
I can promise you that Eric doesn't skip ANY steps. I'm also sure he didn't say that but did say "something like that".

 

[gunsandgunsmithing]

Agreed
I dont know what parameter plays the bigger role but I have worked up a load in 50F weather and had it shoot like crap when it suddenly warms up a week later to 70F

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This is true but while density goes down with temp increase, its not necessarily the same air density over the same temp increase, from day to day etc. Non linear density change over the same temp swing.

Same, tuner or no tuner. These are the challenges to KEEPING up with peak tune.

 

[ELR LVR]

Ok IS a tuner changing your barrel hormonic and seating dept. changing exit timing? To me ( asking for a friend) a tuner would more helpfully on a long barrel and seating dept would be more effective on a short stiff barrel. A lot of talk about hormonic and exit timing

Seating depth is for every length of barrel even a 5 inch 1911
The Seating Depth is Timing your bullets exit timing to the optimum swing/freq of the barrel
The tuner, alters the phase shift of that freq to be back in the optimum timing of your bullets exit
(from what I understand)
someone may expand or correct me if needed since I am simplifying this to keep it short

 

[Bill Norris]

This is true but while density goes down with temp increase, its not necessarily the same air density over the same temp increase, from day to day etc. Non linear density change over the same temp swing.

Same, tuner or no tuner. These are the challenges to KEEPING up with peak tune.

I learned really quick there is no set pattern for any barrel period. No free lunch. One must stay on top of it. However, most of the time the tune will not be very far from where the setting was when tuned. I think this is the area where lots of shooters get carried away with turning the tuner.

 

[gunsandgunsmithing]

Seating depth is for every length of barrel even a 5 inch 1911
The Seating Depth is Timing your bullets exit timing to the optimum swing/freq of the barrel
The tuner, alters the phase shift if that freq to be back in the optimum timing of your bullets exit
(from what I understand)
someone may expand or correct me if needed

Yes! Phase shift! Thank you! You nailed it with those two words that explain so much about tuning. Changing powder charge, for example, does not change frequency but it does change tune! Thank you for being so right and just "getting it"

 

[gunsandgunsmithing]

I learned really quick there is no set pattern for any barrel period. No free lunch. One must stay on top of it. However, most of the time the tune will not be very far from where the setting was when tuned. I think this is the area where lots of shooters get carried away with turning the tuner.

I think you are very right, Bill!

 

[BoydAllen]

Mr Boyd Allen, I remember in 2013 when you noted that Gene Bukys set his tuner in the middle of a node, locks it in, and never moves it, preferring to tune by "normal" methods. In visiting with many top shooters through the years, and many still to this day, they do the same. Matches can be won with or without tuners. Some of the best in the business still prefer no tuner. Some of the best prefer a tuner. I think we would agree, there should be no argument!

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.

 

[BoydAllen]

Technically this is true but its such a small amount that any benefit gets lost in the noise. I know this from vibration analysis testing, so not guessing or hypothesising.

Exact numbers vary with other factors like tuner weight, barrel stiffness and likely even the homogeny of the steel bbl. We plan on testing pre and post cryo bbls in the near future for this reason.

Its tiny in regard to node width. Most every factor to tuning is more significant.

I know its been claimed and its true, just not enough to matter unless its a confidence thing. Which, as we know, does matter but is harder to quantify.

I have a friend who confines his evaluations to looking at groups. He would disagree. I have seen his data. He does a LOT of testing.

 

[gunsandgunsmithing]

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.

That's not at all unusual Boyd, with or without a tuner. There's more to it than just temps. We've touched on it a bit over the last few posts.

 

[JFrank]

I’ve heard exit timing, optimum barrel timing, phase shifting, positive compensation and bending frequencies…to me it’s all just tuning and I’m happy not having to go through all the extra terminology to get a barrel tuned.
If I were to give advice ( and I’m not ) I’d say if a guy wants to succeed go out and put in the work rain shine freeze or snow with or without a sea of flags or a tuner and out work your competition.

 

[Bottom Fodder]

A lot information shared in this tread, I’m not a tuner user for several reasons
So I’m more interested in the thoughts on the seating depth aspect. So if you guys would explain the science behide how actually seating depth changes the exit time. I fully agree that you can tune a load by adjusting seating depth
But what’s the science behide it
Thanks

 

[Tangent]

I don't use a tuner but I've seen the reverse happen. I wondered why my wife's CZ MTR was shooting all over the place and eventually tracked it down to a loose threaded muzzle cap. Tightened it back up and all was well again. So I'm quite sure a tuner will change how a rifle shoots.

 

[Alex Wheeler]

Seating depth has to change exit timing just like other aspects of tuning but its not what we see on target. I can cut a barrel to many different lengths and the bullet will still like its relationship to the lands. I can ship out barrels to a bunch of guys and almost everyone will tune in the same place for seating with the same bullet. So whatever seating depth is doing, its a relationship between the bullet and throat more than the muzzle. Thats why I would prefer to keep up with my seating depth vs using a tuner to stay on it. Some cartridges like a ppc or 30br are very easy on throats and you may never need to. Others like a dasher you may need to chase almost every match.

 

[JEFFPPC]

So an interesting side note. I shoot a Diana 54 Springer air rifle. At 25 yards it was a 2 to 2.5 inch rifle. By tuning the spring and cleaning up some internals it became a 1 inch rifle. I then added a tuner. It now shots 5 shots in the .1s to .2s. Sometimes less. Pellet is what it is, where it is. Yes some shoot better than others maybe more by the length of the pellet than the weight?

 

[tom]

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

 

[ELR LVR]

A lot information shared in this tread, I’m not a tuner user for several reasons
So I’m more interested in the thoughts on the seating depth aspect. So if you guys would explain the science behide how actually seating depth changes the exit time. I fully agree that you can tune a load by adjusting seating depth
But what’s the science behide it
Thanks

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.

 

[NC/Br Shooter]

Tuner is another variable that you have to control. Why add to the fire?

 

[gunsandgunsmithing]

Tuner is another variable that you have to control. Why add to the fire?

The easiest answer is because it allows me to stay in tune and still go pre-loaded, only changing one thing, the tuner. I don't agree that it adds variables, once you get them figured out. To me, it's by far the easiest way to keep up with tune changes. Otherwise, I'd be loading at the range, which adds variables and a bunch more stuff to haul and less time to enjoy shooting a match.

 

[quest450]

Tuner is another variable that you have to control. Why add to the fire?

Oh boy…..trouble in paradise again

 

[ELR LVR]

Tuner is another variable that you have to control. Why add to the fire?

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