More on Barrel Tuners

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pjifl
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Re: More on Barrel Tuners

#76 Postby pjifl » Thu May 24, 2018 9:01 pm

Yes, absolutely correct, Barry. The names shooters have given to many things are in fact incorrect. Bit like the names for 'shooter's mirage' and 'degrees' for sight corrections.
And it is NOT the velocity of the muzzle flicking the projectile that causes havoc, instead it is the direction change of the muzzle that has the main effect.

If an antinode is not quite at the muzzle end but close, it is when the barrel is at maximum deflection when the direction of the muzzle changes most slowly. So you have a wider range of ammo exit speeds having minimum dispersion. Shooter's call this a node and broadening the node. Total misnomer.

As a matter of interest, the animations on Varmint Al's site are excellent BUT ARE ALL WRONG IN ONE ASPECT. The animations show a constant velocity as the muzzle (or other antinode swings back and forth. In fact, the motion slows down a lot at maximum deflection. Just like a pendulum swings fastest near the centre but has slowest speed near max deflection.

The word 'tune' is being used for different processes and all are getting mixed up. And the word 'Damping' is being used incorrectly. And compensation is entirely different.

No wonder it is entirely confusing and no one can make head nor tail of the process and successfully match theory with observed behavior.

Peter Smith.

bruce moulds
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Re: More on Barrel Tuners

#77 Postby bruce moulds » Thu May 24, 2018 10:06 pm

and it gets more complicated.
speed of bullet nodes might vary, but speed of sound nodes are likely constant.
"SUCH IS LIFE" Edward Kelly 11 nov 1880
http://youtu.be/YRaRCCZjdTM

!Peter!
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Re: More on Barrel Tuners

#78 Postby !Peter! » Fri May 25, 2018 12:33 am

pjifl wrote:Yes, absolutely correct, Barry. The names shooters have given to many things are in fact incorrect. Bit like the names for 'shooter's mirage' and 'degrees' for sight corrections.


I think this is a big part of the confusion this area. Once I "decoded" the incorrect names used back to established text book terms it became clear to me.

williada
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Re: More on Barrel Tuners

#79 Postby williada » Fri May 25, 2018 1:13 am

Bruce, Peter and Barry are absolutely correct about the definitions here as you are and shooters have for as long as I have known see the small group as a node. In many minds the peak or a trough on a standing sine wave can be seen as a momentary pause in the phase so in that sense it is like a node where there is minimum amplitude. I prefer to define that as shooter speak, rather than take a lengthy discussion trying to convince people otherwise as it seems to be world wide convention now just like language changes definition. Otherwise taking shooters forward from what they understand and at times it gets very frustrating on a board like this because the topics do require a senior level physics background so apples are not oranges when you get into the nitty gritty. There is plenty out there on Youtube on harmonics if people are interested.

Peter is right about the discussion between harmonics and compensation. Those that quote Litz and Varmint Al have to realize their models can not capture everything although they are excellent. Litz does not consider compensation, something I think DaveMac and I pointed out some years ago. It does not mean they are not excellent teachers because many shooters have to advance from a lower base and their work has facilitated great progress. Varmint Al from my distant memory did not consider closed tube harmonics as a model to explore compared to open tubes although I have not checked the site out for many years, but that was my impression at the time. But at least Al gets people thinking in more advanced ways and has led a revolution in shooting.

What Gyro says about the small percentage gains is correct too. In benchrest that can make a clear winner, but in F Class we tend to shoot for score and don't have the opportunity for multiple sighters and like Gene Begs time to shoot on a crosswind. Gene has had tremendous input and has good reason for his shooting preference which in my view is linked to bullet lift and wind strength readability. In F Class time allocation and number of shots fired is different.

There are lots of tangents to go off here, that a tuner will change group shape to more effective in different wind vectors. People should try it and take notes because each setup is different in scale of movement. I posted an image of Ecomeat' groups some time back of work we were doing with a tuner. To achieve this the rifle was tuned beforehand without the tuner, then movements were mapped. These need to be placed on your shooting box to jog the memory.

The speed of sound does vary with temperature.

An internal taper will bunch the different frequencies just like an external taper. But the problem still remains as to where that bunch occurs and what does it do to muzzle direction and shape. It is a separate issue when the tighter taper .0004" at the end of the barrel starts from whether the heat generated from friction mitigates against clashing returning vibrations altering bore size. A fast string heats the barrel too and sometimes we can associate that with a good group. Heat tends to reduce vibration and therefore distortion. Another reason I went to faster burning powders such as 2209 in the 7mm Saum. Getting the size right is trial and error, but tests I did with bore size indicated dispersion increased where the bore size was greater than .0005" of the bullet diameter. I found the velocity on tighter bores actually decreased and merely increased pressure. The increase in pressure resulted in the swaging of the projectile at the breech and the energy was used there rather than in the forward movement of the projectile. The base of the bullet still sets up fairly well (as gas pressure expands its base) with a tiny amount of oversize. So its not something to worry about excessively so long as in bore yaw is not created with a sloppy chamber which is the real culprit. A skilled armouror should slug the barrel and lap accordingly. Variations in bore size are ruinous to accuracy unless they taper very slightly towards the muzzle if at all.

Even if we know all the factors and can identify multiple sources of vibration each with different timing and each with their own sub frequencies there remains potential for distortion of each of their own fundamental frequencies. There are a lot of things happening and the paper is the best guide for working backwards to eliminate problems if they are significant.

The gain twists are a different ball game from my experiments, where some were made and some went the other way. The first problem is the jacket which must respond to the driving side of the rifling. I don't think a canted land will work here from experience. The cut in the jacket made by the rifling varies as the driving angle is accommodated. This was discussed a few years ago here. In high powered rifles the gain was best to finish a few inches before the muzzle and was constant in the last few inches rather than run from breech to muzzle. I can understand why Boyer's rifle with the tiniest of gains worked because he was not distorting the jacket sufficiently to offset the benefits, let's call it marginal propensity in theory to improve with gain twist at high velocity. The resources to find out what works is beyond the scope of the ordinary shooter and not worth worrying about for F Class where the wind or light in a long string over multiple distances is humongously more important.

I think I posted a gain 7mm twist some years ago with mapped groups. The observation being the tightest group correlated with minimum extreme spread. There was also a torque factor that came in with an offset stock. This demonstrated to me the need for absolute symmetry in stock design aligned with the centre of gravity. The greater the offset the greater the slant of groups. This is a separate torque factor from that was shown in Varmint Al's early work and pinching of barrels. That is not really significant in thick barrels and if it occurs it corresponds to extreme spread and group enlargement.

So if we go to the extent of minimizing every last nuance, then perhaps zeroing at 140 yards could separate out imagined effects when most projectiles have gone to sleep. I would advocate any construction of a new "blow off range" be a minimum of 140 yards if people are serious about rifle tuning.

!Peter!
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Re: More on Barrel Tuners

#80 Postby !Peter! » Fri May 25, 2018 2:44 am

I must confess I had to find my high school physics text to start with.

bruce moulds
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Re: More on Barrel Tuners

#81 Postby bruce moulds » Fri May 25, 2018 8:54 am

thank you williada and others for input into this and the other recent tuner thread.
some thoughts from the real world of an average guy.
first of all, litz is a marketer, and of necessity has to appeal to the widest market for profit.
evidence of this includes referring to wind deflection as wind drift, just because the average bonehead thinks that way.
doing such things hinders rather than helps the great unwashed.
i personally have great trouble with any physics, let alone advanced.
i also have a limited budget, and limited time.
this precludes multiple barrels and endless testing.
more thought can minimize above, but there are limitations in that area.
1000 and 600 yd br shooters can use compensation tuning to get super groups, atmospheric conditions allowing, because they shoot at 1 range, but with 1 barrel, an fclass shooter must go the extra mile to shoot well at all ranges.
today you have to shoot well at all ranges to have a chance, as the standard at the top has become very high.
in a real word scenario, where do you go from here?
firstly, recognize accuracy priorities.
tune as best you can for the biggest issue, because that is where you will get the biggest benefit.
then go down the scale of priority with fine tuning.
there are no free lunches in this. just thank god , because those prepared to think and act will end up in front of the free lunch brigade.
i have always done ladder tests at 500, after seating depth tests at 100.
this is not a bad start, but is just that, a start, not the end.
from there i used club shoots to shoot an experiment against a known best, an sometimes altered things based on this.
so where does this leave tuners.
as we know, the lowes velocity s.d. loads do not always group as well as some with higher s.d.
this reflects nodes/antinodes, and/or compensation.
the temptation now is to shoot 3 shot groups at 150 yds and compare the (for want of a better term) sine waves, but take great notice of s,d.
of course you need to shoot enough shots to get a valid s.d., meaning that thought has to go into this.
ultimately, a load with minimal s.d. will shoot best at all ranges, and particularly long ranges, if in tune.
this might be the biggest job the tuner can do.
so what is the best tuner, and its best modus operandi :?:
and this does not include vert issues due to lighting and air movement condition.
and there is the other thing to master - wind DEFLECTION.
keep safe,
bruce.
"SUCH IS LIFE" Edward Kelly 11 nov 1880

http://youtu.be/YRaRCCZjdTM

Gyro
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Re: More on Barrel Tuners

#82 Postby Gyro » Fri May 25, 2018 9:21 am

Bruce dont forget Mr Litz did not come down in the last shower. I would frankly suspect he is humoured by much of what he hears and reads !

This thread seems to be approaching more common sense with discussion about the simpler but perhaps more 'knowable' dynamics at work here. I would like to know more about the effects of different light on the atmospherics ?

bruce moulds
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Re: More on Barrel Tuners

#83 Postby bruce moulds » Fri May 25, 2018 10:23 am

further thoughts from the perspective of the average grunt.
i like the look of the huntsman tuner, but such designs are really impractical in terms of needing a new safe, gun boxes, etc due to length.
rubber containing tuners look interesting.
backboring the barrel - diameter and length of bore - actual barrel length after doing so - keeps tuner away from rifled section.
such things as purdey tuning combined with a tuner.
ringing barrels with a hammer.
barrel diameters for best tuning, and tuner weights that match.
keep safe,
bruce.
"SUCH IS LIFE" Edward Kelly 11 nov 1880

http://youtu.be/YRaRCCZjdTM

wsftr
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Re: More on Barrel Tuners

#84 Postby wsftr » Fri May 25, 2018 7:25 pm

bruce moulds wrote:thank you williada and others for input into this and the other recent tuner thread.
1000 and 600 yd br shooters can use compensation tuning to get super groups, atmospheric conditions allowing, because they shoot at 1 range, but with 1 barrel, an fclass shooter must go the extra mile to shoot well at all ranges.a
today you have to shoot well at all ranges to have a chance, as the standard at the top has become very high.
bruce.


Just out of curiosity - how would you define "shoot well at all ranges" with respect to moa vertical. We have to assume that score is primarily derived from wind reading....You can have high x count but a relatively poor score. i.e a precise rifle but poor wind calls
Would you say an average of .5 moa vertical on any given day at any range (300 - 1000) or would you define that with a smaller number?

bruce moulds
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Re: More on Barrel Tuners

#85 Postby bruce moulds » Fri May 25, 2018 7:56 pm

wsftr,
i am talking of the 1 barrel shooter.
having experienced the good and bad of compensation nodes, it is obvious that such a barrel is not an all range tool, unless perhaps you can get a load for each range.
what a bore.
so in moa vert, it must be tuneable to acceptable at all ranges.
of course to win on the day, accuracy requirement will vary with bending light and wind conditions, and scores will reflect these things.
but looking at scores lately, you might in good conditions shoot a 60.6 and come 9th or worse.
so the goal should be to better 0.5 moa to allow for less than perfect wind calls. the wider target is the best one.
we must accept that this sport is about wind reading as well as accurate gear, and that is another subject.
keep safe,
bruce.
"SUCH IS LIFE" Edward Kelly 11 nov 1880

http://youtu.be/YRaRCCZjdTM

williada
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Re: More on Barrel Tuners

#86 Postby williada » Fri May 25, 2018 8:45 pm

I would demand a quarter minute rifle in the right hands that may let out just a tad over the middle ranges. Its doable. It may mean sorting through a number of barrels. I know that if a barrel does not perform within tight specifications for Boyer, he does not try to adapt it,it is gone. Many here do not have that luxury and the right tuner forward of the muzzle may correct some of the issues. Of course the smithing has a lot to do with the quality of the natural performance of a tube. Take your gear to someone who understands the finer points and pay the person for their knowledge.

wsftr
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Re: More on Barrel Tuners

#87 Postby wsftr » Sat May 26, 2018 1:49 pm

bruce moulds wrote:wsftr,
i am talking of the 1 barrel shooter.
bruce.


Yes I am a one barrel shooter :)

williada wrote:I would demand a quarter minute rifle in the right hands that may let out just a tad over the middle ranges. Its doable. It may mean sorting through a number of barrels. I know that if a barrel does not perform within tight specifications for Boyer, he does not try to adapt it,it is gone. Many here do not have that luxury and the right tuner forward of the muzzle may correct some of the issues. Of course the smithing has a lot to do with the quality of the natural performance of a tube. Take your gear to someone who understands the finer points and pay the person for their knowledge.


Do you mean a 1/4moa rifle at the load dev range or at any distance (300 - 1000) on any given day you would expect 1/4 moa vert during a match?

Audax
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Re: More on Barrel Tuners

#88 Postby Audax » Sat May 26, 2018 1:56 pm

I am glad that one got the cut...wonder how many more were in the box...?
https://www.ganderoutdoors.com/product/ ... &from=grid

Gyro
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Re: More on Barrel Tuners

#89 Postby Gyro » Sat May 26, 2018 2:46 pm

wsftr wrote:
bruce moulds wrote:wsftr,
i am talking of the 1 barrel shooter.
bruce.


Yes I am a one barrel shooter :)

williada wrote:I would demand a quarter minute rifle in the right hands that may let out just a tad over the middle ranges. Its doable. It may mean sorting through a number of barrels. I know that if a barrel does not perform within tight specifications for Boyer, he does not try to adapt it,it is gone. Many here do not have that luxury and the right tuner forward of the muzzle may correct some of the issues. Of course the smithing has a lot to do with the quality of the natural performance of a tube. Take your gear to someone who understands the finer points and pay the person for their knowledge.


Do you mean a 1/4moa rifle at the load dev range or at any distance (300 - 1000) on any given day you would expect 1/4 moa vert during a match?


Good question. What i do know is shooters are always scrupulously honest about what thier gun did when they grouped it ... lol.

williada
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Re: More on Barrel Tuners

#90 Postby williada » Sat May 26, 2018 10:17 pm

Guys there was a publication written by Warren Page called, "The Accurate Rifle", written so long ago who was quoting the bench standard of 1/4 minute of that era. Seeing a few posters have referred to Boyer etc, in a different discipline to ours to grasp the value of a rifle's capability, the 1/4 minute standard is old hat where shots are measured centre to centre.

At my short range tuning distance of 140 yards, I wouldn't accept anything greater from a tuned rifle from those that went through several development programs we have run in the past. At long distance, we generally refer to elevation in F Class in minutes of angle as a reference for performance. Holding quarter minute of angle elevation even at one thousand yards is not a hard thing to do on a regular basis. Such a rifle gives the shooter a buffer for wind or enables the shooter to aim off centre so conditions that can escape the shooter while aiming can deflect in; and of course light effects both diffraction and brightness cause the shooter to aim in the wrong place. The latter has nothing to do with capability. The rifle's capability does not change, only the shooter's ability to interpret conditions. That's the honesty part and skill level.

Now Gyro why do you suppose, I am happy with a barrel that lets out in the middle distance, performs well at 300 and holds up at the longs?


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