Moderator as barrel tuner

[Popsbengo]

2 hours ago, Montey said:

This thread is about  barrel tuners something I will be playing with on the two new rifles I've got coming as soon I'm able to pick them up. My point is does one develope a load and then tune it with the tuner or is it that the tuner becomes a factor to be moved with every  change and step of the load development? I hope that makes sense? I would gues it's a case of set the tuner in the middle  develop a load and then tune it using the tuner? As Mick has built two identical rifles for himself there will be a lot of load  development already there and I will be following his lead however I still find it an interesting question.

 

I think Big Al has covered that well in an earlier post in this thread.

[terryh]

41 minutes ago, Twodogs said:

From my experience with .22 it seems to be find the best round then introduce the tuner. I appreciate it might be a totally different ballgame with CF. 
 

This has been my approach in the past. Find the ammunition your rifle likes then adjust with the tuner. Never played with CF tuners.

thing that I’ve had in the back of my mind re 22rf is do you find the ammunition without the tuner on then add tuner or have it present from the get go but do not do any adjusting?

[1066]

1 hour ago, terryh said:

This has been my approach in the past. Find the ammunition your rifle likes then adjust with the tuner. Never played with CF tuners.

thing that I’ve had in the back of my mind re 22rf is do you find the ammunition without the tuner on then add tuner or have it present from the get go but do not do any adjusting?

My thought re 22lr is do every thing you can first, bedding, trigger, cleaning regime etc, then ammo selection, then when you think you have reached the potential of the rifle/ammo combination, add your tuner and try and improve on your best results. (Not a couple of 3 shot groups).

[terryh]

Hi Allen,

Currently leaning towards this approach, pointless Trying to drag the last few ‘mm’ out of the rifle using a tuner if the foundation’s are iffy. I actually find shooting a 22rf consistently quite a challenge - well it feels that way 😉.

Just sorting a new 22rf rifle which will wear a (particle) tuner and plan on a decent amount of time in a local 100m indoor range testing ammunition (when things arrive and open, respectively ).

Looking at the LR 22rf comes as a challenge if I can get my poo in one sock so sorting all the detail is a prerequisite  😂

 

[1066]

39 minutes ago, terryh said:

Hi Allen,

Currently leaning towards this approach, pointless Trying to drag the last few ‘mm’ out of the rifle using a tuner if the foundation’s are iffy. I actually find shooting a 22rf consistently quite a challenge - well it feels that way 😉.

Just sorting a new 22rf rifle which will wear a (particle) tuner and plan on a decent amount of time in a local 100m indoor range testing ammunition (when things arrive and open, respectively ).

Looking at the LR 22rf comes as a challenge if I can get my poo in one sock so sorting all the detail is a prerequisite  😂

 

I'd love access to a 100m indoor range to play with the rimfire. I have a Sako Finnfire fitted with a Lilja match barrel, it's fairly accurate when fed good ammunition as you would expect. I shoot it in short range benchrest comps but always feel it should do better. What I have recently found is, against my natural inclination, if I hold it as hard and tight as I can, it shoots a blinder, just like I think it should, certainly as good as my BSA International. Although nothing to do with tuners it does show just how getting the best out the .22lr is an art rather than a science.

[brown dog]

Just read this.... any thoughts?

"I tried them before and turned to something similar. Instead of using the limbsaver deresonator, I got better results with the following procedure:
Hang the rifle from the buttplate. In a quiet environment, tap the barrel with your index finger along its length, and listen to the tappping noise with your ear close to the barrel, although not touching it.
What you are looking for is for a spot that makes a dull noise about 6 inches from the muzzle.
Mark the spot with a texter.
Next, keep tapping towards the chamber end and look for the spot where the noise is the loudest. Mark with a texter.
Keep on tapping back to the chamber end looking for another dull noise point. Mark with a texter.
Then I use a product called megasorber which are adhesive sheets of a very efficient polymer that converts vibration into heat. On the other side of the adhesive sheet, you have a layer of aluminium foil which acts as an heat sink to dissipate said heat.
http://www.megasorber.com/soundproofing-products/vibration-dampeners/constrained-layer-damping-sheet.html
I cut a 4 inch long section of that sheet and stick it with its mid section on the spot on the barrel that you marked as the one with the loudest vibration in a way as to surround completely the circumference of the barrel.
This will really subside the travelling wave mentioned on http://www.the-long-family.com/OBT_paper.htm.
I felt a good improvement in accuracy on about 20 out of20 of my target rifles that I did this procedure to.
The point which makes the loudest tapping noise is the one where the amplitude of that travelling wave is the highest allowing the damping to work at its best.
That frequency that you are trying to dampen is shaped like a donut that travels down the barrel at about 20 000 fps, disturbing the bullet according to the obt article 8 times on a 24 inch barrel. If you manage to dampen 40% of that vibration at each pass, the projectile will only meet that donut once and at 20% of the amplitude.
Really worked for me."

[Popsbengo]

1 hour ago, brown dog said:

Just read this.... any thoughts?

"I tried them before and turned to something similar. Instead of using the limbsaver deresonator, I got better results with the following procedure:
Hang the rifle from the buttplate. In a quiet environment, tap the barrel with your index finger along its length, and listen to the tappping noise with your ear close to the barrel, although not touching it.
What you are looking for is for a spot that makes a dull noise about 6 inches from the muzzle.
Mark the spot with a texter.
Next, keep tapping towards the chamber end and look for the spot where the noise is the loudest. Mark with a texter.
Keep on tapping back to the chamber end looking for another dull noise point. Mark with a texter.
Then I use a product called megasorber which are adhesive sheets of a very efficient polymer that converts vibration into heat. On the other side of the adhesive sheet, you have a layer of aluminium foil which acts as an heat sink to dissipate said heat.
http://www.megasorber.com/soundproofing-products/vibration-dampeners/constrained-layer-damping-sheet.html
I cut a 4 inch long section of that sheet and stick it with its mid section on the spot on the barrel that you marked as the one with the loudest vibration in a way as to surround completely the circumference of the barrel.
This will really subside the travelling wave mentioned on http://www.the-long-family.com/OBT_paper.htm.
I felt a good improvement in accuracy on about 20 out of20 of my target rifles that I did this procedure to.
The point which makes the loudest tapping noise is the one where the amplitude of that travelling wave is the highest allowing the damping to work at its best.
That frequency that you are trying to dampen is shaped like a donut that travels down the barrel at about 20 000 fps, disturbing the bullet according to the obt article 8 times on a 24 inch barrel. If you manage to dampen 40% of that vibration at each pass, the projectile will only meet that donut once and at 20% of the amplitude.
Really worked for me."

Having read the Chris Long article (which I enjoyed) he seems to be suggesting that longitudinal vibration in the barrel can be used to time/tune OBT to contribute to repeatability by presenting a 'tighter' muzzle condition at the crown and harmonic effects on early stage combustion.  Your quoted writer seems to be suggesting damping this down is a good thing - that seems to be counter to the C.L. theory.

Having said that I'm not convinced by the Long theory but I can't deny the practical outcome - if it works, it works. Much of the great strides in Victorian engineering were practical, empirical method,  they left the science to come along after and explain why.

If I understand correctly barrel harmonic tuners are tuning transverse vibration (like a ruler over the edge of a desk),  so Long's theory doesn't apply.

[1066]

Ringing the barrel is easy to do and certainly shows where the null points are, and probably shows where a barrel dampener device (Limbsaver) would have most effect. A light dusting of talc powder along the barrel then rapping the barrel with a rubber handled screwdriver give a visual indicator of where the null points are too.
This is my dirt cheap "lookalike" limbsaver. It's actually a suspension bumpstop, less than a fiver from Ebay/China. This is fitted to my spare Finnfire varmint barrel (22mm) I've not tried it yet but can't see any reason it wouldn't work just as well as a pukka limbsaver. Unfortunately they are yellow rubber, so sprayed this one with car bumper paint.

[Popsbengo]

3 minutes ago, 1066 said:

Ringing the barrel is easy to do and certainly shows where the null points are, and probably shows where a barrel dampener device (Limbsaver) would have most effect. A light dusting of talc powder along the barrel then rapping the barrel with a rubber handled screwdriver give a visual indicator of where the null points are too.
This is my dirt cheap "lookalike" limbsaver. It's actually a suspension bumpstop, less than a fiver from Ebay/China. This is fitted to my spare Finnfire varmint barrel (22mm) I've not tried it yet but can't see any reason it wouldn't work just as well as a pukka limbsaver. Unfortunately they are yellow rubber, so sprayed this one with car bumper paint.

great tip

[ds1]

If you consider harmonics/ vibration induce heat then a structured barrel makes a lot of sense.

 

[1066]

Having rang quite a few barrels, pipes, cleaning rods etc. etc. in the course of experiments, it's apparent they all follow a fairly predictable pattern no matter what the length or diameter (taper throws a spanner in the works).

If you get a flexible rod of any length and hold it at one end and wobble it side to side you will see the null points quite clearly, I find this is just over 3/4 the length of the rod. If you then clamp the rod in a vice and ring it you can hear the null point in the same place. If you tap the rod anywhere but on the null points the rod will ring, tap the null points and it's dead.

Now if you tap the rod to ring it and touch it anywhere but on the null point the ringing stops instantly (Just like touching a bell) If you touch it on the null point the rod keeps ringing.  How that helps in practice I really don't know, it could do with a lot more testing under controlled conditions. It strikes me the best starting place for the dampener would be just about halfway down the barrel, however this will often not be possible because of the woodwork. A good quality barreled action in a return to battery jig and a tunnel range is required here I guess.

[brown dog]

1 hour ago, Popsbengo said:

Having read the Chris Long article (which I enjoyed) he seems to be suggesting that longitudinal vibration in the barrel can be used to time/tune OBT to contribute to repeatability by presenting a 'tighter' muzzle condition at the crown and harmonic effects on early stage combustion.  Your quoted writer seems to be suggesting damping this down is a good thing - that seems to be counter to the C.L. theory.

Having said that I'm not convinced by the Long theory but I can't deny the practical outcome - if it works, it works. Much of the great strides in Victorian engineering were practical, empirical method,  they left the science to come along after and explain why.

If I understand correctly barrel harmonic tuners are tuning transverse vibration (like a ruler over the edge of a desk),  so Long's theory doesn't apply.

I agree, there's a slight conflation of waves, I'm not sure I follow how transverse nodes affect longitudinal waves, but... I quite 'like' the thinking g about longitudinal waves effect on the muzzle condition, and I'm quite struck by the observation that the bullet has gone before transverse can 'really get going'.... perhaps less so in a rimfire   so... given that we can't adjust barrel time via charge weight on a rimfire, how else might we 'tune' the timing... with a chosen round, change barrel length to suit the round's barrel time... for tgt  rounds all just Subsonic, that would suggest there are optimal barrel lengths to hit each reflected wave sweet spot, and by extension, there will be barrel lengths that won't shoot as well...by his theory, that could be calculatable and would apply irrespective of barrel weight etc... so (made up numbers) for match ammo, 17", 18.5", and 20" could all be optimal, with any value in between less optimal.    So....on a fixed sub-optimal barrel length are the dampers achieving their main effect via transverse or longitudinal damping? Would a better effect be achieved by matching barrel length to a particular round?   

Or put another way, if Long's theory holds water, for a rimfire with match ammo... barrel length does affect accuracy.

 

(And I'm not sure where that all leaves tuning weights which clearly, empirically also have an effect! 😂🤔)

[terryh]

Allen.

Agree on ringing barrels ref your talc method, this is how you sort out the location for the front rest on a BPCR (sacrilege- 'you rest the barrel' 😉 ).

As to what's doing what? - lot of ideas and things to consider, think the relatively slow barrel time for 22rf does play into this, few high speed videos on the InterWeb of rifles being fired and the bullet 'appears to be out of the barrel before the barrel moves.

You see the dogma re. 22rf barrel length 'what's the point beyond X" all the powders burnt' etc. but from reading the things folks are pushing re. accuracy and longer range with 22rf's then this plus the age old 1:16" twist (or there abouts) is falling down. 

That tuners do something and improve accuracy - been shown for rf a good while.

Will try some large section O seals on the dead spot when I'm playing with the new rifle.

T

[Popsbengo]

14 hours ago, brown dog said:

I agree, there's a slight conflation of waves, I'm not sure I follow how transverse nodes affect longitudinal waves, but... I quite 'like' the thinking g about longitudinal waves effect on the muzzle condition, and I'm quite struck by the observation that the bullet has gone before transverse can 'really get going'.... perhaps less so in a rimfire   so... given that we can't adjust barrel time via charge weight on a rimfire, how else might we 'tune' the timing... with a chosen round, change barrel length to suit the round's barrel time... for tgt  rounds all just Subsonic, that would suggest there are optimal barrel lengths to hit each reflected wave sweet spot, and by extension, there will be barrel lengths that won't shoot as well...by his theory, that could be calculatable and would apply irrespective of barrel weight etc... so (made up numbers) for match ammo, 17", 18.5", and 20" could all be optimal, with any value in between less optimal.    So....on a fixed sub-optimal barrel length are the dampers achieving their main effect via transverse or longitudinal damping? Would a better effect be achieved by matching barrel length to a particular round?   

Or put another way, if Long's theory holds water, for a rimfire with match ammo... barrel length does affect accuracy.

 

(And I'm not sure where that all leaves tuning weights which clearly, empirically also have an effect! 😂🤔)

I think the C.L. theory is maximum and minimum nodes from additive and destructive interference.  He uses  RF transmission line EM waves as analogy.  I'm not convinced that's a valid analogy as EM waves are transverse. (I trained as a radio & telecoms engineer).    I'm happy to be corrected - it's been a long time.

It's more likely (according to Long) to be timings of the longitudinal wave bouncing back and forth at the speed of sound in steel, therefor one times the bullet to arrive as the maximum wave compression at the muzzle.  These compression waves also retard or increase bullet transit time in the barrel by increase and decrease in friction - this affects combustion progress by modulating the gas pressure.

It occurred to me that if Chris Long's theory is correct then fitting a muzzle brake will have an affect on the crown by increasing the local stiffness by increasing the cross section of steel. 

I'm a little skeptical but it's intriguing 

 

[brown dog]

1 hour ago, Popsbengo said:

 

It's more likely (according to Long) to be timings of the longitudinal wave bouncing back and forth at the speed of sound in steel, therefor one times the bullet to arrive as the maximum wave compression at the muzzle.  These compression waves also retard or increase bullet transit time in the barrel by increase and decrease in friction - this affects combustion progress by modulating the gas pressure.

 

 

My nuance on that, was that I read it as saying 'don't have shot exit when the doughnut is at the muzzle' ... which, as you say reflects up and down the barrel at the speed of sound in steel.   And from that, since we can't tweak barrel time through charge or seating manipulation in a rimfire, means that some barrel lengths will be optimal for a match round, and some will be not... each step length aligning with when the doughnut is away from the muzzle.

I didn't pick up on a gas/pressure change.. I'll reread, but that strikes me as so infinitesimally small (volume change vs overall volume) that I would struggle to buy it as an idea

[Popsbengo]

3 minutes ago, brown dog said:

My nuance on that, was that I read it as saying 'don't have shot exit when the doughnut is at the muzzle' ... which, as you say reflects up and down the barrel at the speed of sound in steel.   And from that, since we can't tweak barrel time through charge or seating manipulation in a rimfire, means that some barrel lengths will be optimal for a match round, and some will be not... each step length aligning with when the doughnut is away from the muzzle.

I didn't pick up on a gas/pressure change.. I'll reread, but that strikes me as so infinitesimally small (volume change vs overall volume) that I would struggle to buy it as an idea

So what we need is an adjustable length barrel 😁.  It would be possible to increase a non-rifled section, say at the breech end, with threaded sections of differing lengths.  Paradox rifling meets adjustable length ?  😉

[1066]

15 minutes ago, Popsbengo said:

So what we need is an adjustable length barrel 😁.  It would be possible to increase a non-rifled section, say at the breech end, with threaded sections of differing lengths.  Paradox rifling meets adjustable length ?  😉

Isn't that what, in effect, an adjustable tuner in front of the muzzle does?

[brown dog]

😂 my point was, if this doughnut theory is correct...

22 Match ammo is all the same mv (give or take)

So... it should be possible to work out which barrel lengths will have shot exit when the doughnut is away from the muzzle.

So, made up numbers, 16, 17.5, 18.25, 19, 23.5   could all be optimal lengths  ... with other lengths less optimal, and some lengths positively to be avoided.

At a doughnut-optimal length, the tuner could then be employed to do whatever voodoo it's doing.

... just spitballing.!

I just got rid of a cz455 precision that simply didn't want to shoot... it had every ingredient that should have made it work, but it just didn't want to..it was 'unforgiving' and would just randomly throw shots out of a group that otherwise felt good,  and sounds much like Allen's finnfire  .... what if both barrels were at a lengths that mistimed the harmonics of the donut? 

In contrast, I replaced it with a cz452 cut to 17".... and it wants to put every bullet in the same hole.

....this is not to be confused with 'optimal mv length' where 14" seems to be the value that's routinely trotted out, I'm focusing on the harmonics of the doughnut... and timing shot exit to take place when the doughnut is away from the muzzle as it reflects back and forth along the barrel

...if there's any value in the doughnut theory🤔😂😂

[Popsbengo]

1 hour ago, 1066 said:

Isn't that what, in effect, an adjustable tuner in front of the muzzle does?

not quite, the muzzle tuner doesn't affect the proposed longitudinal wave as the crown is still n length whatever the tuner adjustment.  It does affect transverse waves by adding mass/distance.

I think. 🙂

 

[Popsbengo]

29 minutes ago, brown dog said:

😂 my point was, if this doughnut theory is correct...

22 Match ammo is all the same mv (give or take)

So... it should be possible to work out which barrel lengths will have shot exit when the doughnut is away from the muzzle.

So, made up numbers, 16, 17.5, 18.25, 19, 23.5   could all be optimal lengths  ... with other lengths less optimal, and some lengths positively to be avoided.

At a doughnut-optimal length, the tuner could then be employed to do whatever voodoo it's doing.

... just spitballing.!

I just got rid of a cz455 precision that simply didn't want to shoot... it had every ingredient that should have made it work, but it just didn't want to..it was 'unforgiving' and would just randomly throw shots out of a group that otherwise felt good,  and sounds much like Allen's finnfire  .... what if both barrels were at a lengths that mistimed the harmonics of the donut? 

In contrast, I replaced it with a cz452 cut to 17".... and it wants to put every bullet in the same hole.

....this is not to be confused with 'optimal mv length' where 14" seems to be the value that's routinely trotted out, I'm focusing on the harmonics of the doughnut... and timing shot exit to take place when the doughnut is away from the muzzle as it reflects back and forth along the barrel

...if there's any value in the doughnut theory🤔😂😂

OK, my brain is hurting now 😁

I have a CZ455 16" and it shoots very well indeed but only RWS Rifle Match (330m/s 40gr).  Absolutely hates Eley.

 

[terryh]

....and you tune the barrel length to the MV to find the next batch you buy has a different MV 😨 it must be adjustable IMHO

If you are looking at a bulge wave (sort of reverse peristalsis if you like) could you put a clamp on the barrel (like a scope ring design item) that messes with the bulge wave, a tuner for longitudinal waves as opposed to the barrel end tuner trying the mess with the sinusoidal waves?

....gosh we are out into the bleachers now 😯

T

[1066]

23 minutes ago, terryh said:

....and you tune the barrel length to the MV to find the next batch you buy has a different MV 😨 it must be adjustable IMHO

If you are looking at a bulge wave (sort of reverse peristalsis if you like) could you put a clamp on the barrel (like a scope ring design item) that messes with the bulge wave, a tuner for longitudinal waves as opposed to the barrel end tuner trying the mess with the sinusoidal waves?

....gosh we are out into the bleachers now 😯

T

Are you thinking this sort of thing?

[brown dog]

21 minutes ago, terryh said:

....and you tune the barrel length to the MV to find the next batch you buy has a different MV 😨 it must be adjustable IMHO

If you are looking at a bulge wave (sort of reverse peristalsis if you like) could you put a clamp on the barrel (like a scope ring design item) that messes with the bulge wave, a tuner for longitudinal waves as opposed to the barrel end tuner trying the mess with the sinusoidal waves?

 

 

Would batch to batch mv variance be significant enough to change barrel time enough, if your barrel length is at a wave relectivity sweetspot?  There'd probably be a bit of 'forgive' either side, much like the charge variance forgiveness postulated for OCW ?

I think the clamp could work, but it'd need to be a damper...   If 'hard' , I think it'd risk it's own reflectivity, refraction on far side etc?  A clamp applying a wrap of shock absorbing material could do it?

[brown dog]

6 minutes ago, 1066 said:

Are you thinking this sort of thing?

Yup, if the Al tube is holding a damping material, to my mind.   

Is that yours?

[brown dog]

1 minute ago, brown dog said:

Yup, if the Al tube is holding a damping material, to my mind.   

Is that yours?

Thinking on.... that's sort of what a tight fitting limbsaver is ?