TargetTalk

patriot wrote: So if it is only the weight, why does the length of the tuner matter? ... or the barrel length independent of the profile? Why does the nearly 30 inch barrel on my mini-palma shoot so well?

Mark.

Mark, did I say it was only the weight? As to the barrel profile, I believe that Guy Starik asks for this information, in addition to length, when ordering a tube, so he at least considers it a factor somewhere. As I wrote yesterday, I don't understand or claim to understand the details of how tubes and weights change vibration, but Physics was never my strong suit.

Tim S wrote:

patriot wrote: So if it is only the weight, why does the length of the tuner matter? ... or the barrel length independent of the profile? Why does the nearly 30 inch barrel on my mini-palma shoot so well?

Mark.

Mark, did I say it was only the weight? As to the barrel profile, I believe that Guy Starik asks for this information, in addition to length, when ordering a tube, so he at least considers it a factor somewhere. As I wrote yesterday, I don't understand or claim to understand the details of how tubes and weights change vibration, but Physics was never my strong suit.

The questions are not directed toward you Tim or others that say profile is a factor. I'm trying to understand what the PRX method tells us.

Mark

Good morning Mark:

I certainly appreciate your approach, and I meant no disrespect in the previous post. I have always appreciated your posts.

I am afraid I fall into the "Joe Dirt" subset on the subject. Although vibration analysis is something we do in my field often, the specific model and variables involved within a rifle as the detonation starts and movement is initiated is difficult to replicate with certainty. All of my personal experience is unfortunately speculative, based primarily on testing alone.

It makes sense to me that the overall length of the cantilever would be a means to control the consistency and or amplitude of the movement at some midpoint (crown). It also makes sense to me that the movement (or subtraction / addition) of any mass would do the same. And I think, drawing on the experiences of other successful shooters, that both methods are proven to do something....whatever that is!! LOL

I think Bryan asked in a previous post if the addition / subtraction of the front sight was significant, and my answer would be absolutely yes. Not only is that much mass significant, but in my opinion the position must me accuractly replicated. I have also found that the position is more critical if using an extension tube (the effects are magnified as the distance from the crown increases). I, like many shooters now, hang the front sight under the tube in a position that mirrors iron sight use.

For me though, it has been difficult to completely validate Tony's theories (based on the PRX formula and overall length), just because as I shortened the extension tube, I was also removing or shifting mass - so it's hard to quantify which variable was actually more significant. Something is happening, so I guess the Joe Dirt in me says well, that's enough!

Thanks for the conversation!

Kev

PS.....I have never thought the use of a tuner mandatory. If you have unlimited time and patience, the manipulation of the crown position accomplishes the same thing IMHO. You would be amazed how much impact the removal of a few tenths of barrel length has on accuracy potential. It makes me wonder how many really great barrels there out there that perform poorly just because the crown is not positioned optimally.

Tim S wrote: As to the barrel profile, I believe that Guy Starik asks for this information, in addition to length, when ordering a tube, so he at least considers it a factor somewhere.

Tim, I emailed Guy Starik last week asking about barrel diamemter as my barrel is stepped down at the muzzle and woundered if he needed both diameters to work out mass etc, however it turns out he only needs muzzle diameter in order to make the tubes clamp the correct size to fit. I dont get the PRX principle, I've calcuated for my 27" barrel and the results were a tuner of 25cm, but guy sells them at 19 or 32 cm. If 25cm is correct why offer two lengths? I also dont get the node principle as that wouldn't allow for variations in ammo speed.

Don't get me wrong I'm sold on the idea of one and will be ordering one in the next few days from Guy, I like the adjustment available with the long foresight rail vs bee sting's single mounting point at the very end, although their micrometer scalling is very usefull. Guy's tuner also appears to be much lighter than the Bee Sting.

The way it makes much more sense to me is in comparing the recoil movement of the muzzle to a pendulum. By adding weight you slow the acceleration of the muzzle and by adding length (moving the tuner weight) you increase the amplitude whilst reducing the frequency. The 'tune point' would then be the point would be then when you've created the perfect frequency curve to put differant speed ammo into the same POI. Fast rounds leaving the muzzle towards the lower part of the curve and a slower round leaving later when the muzzle is slightly higher. Considering the barrel as the string on the pendulum would also explain why the barrel diameter would have no effect. I'm in no doubt that the barrel does vibrate and that standing waves are set up in the barrel however I would wounder if these all occur after the bullet has left the barrel, it is after all very close to the speed of sound when it leaves the muzzle. I guess the only way to find out is to blag an ultra high speed camera and film the muzzle movement after the round is ignited, any uni students reading this?

kevin nevius wrote:It makes me wonder how many really great barrels there out there that perform poorly just because the crown is not positioned optimally.

Kevin - I'm still quite new to this so forgive me for asking (and its off topic) but isn't the best crown position decided on were the barrel slugs at the tightest?

cheers Bryan

Bryan,
I don't sell the tubes in 2 lengthens....(19 and 32cm).
I'm using 2 different harmonies to get the 2 lengthens. One of the harmonies will give about 19cm+-1.5cm, and the other harmoney will give about 32cm,+-2cm,depending on barrel length.
There is another harmoney that Tony gave me which gives about 25cm,+-1.5cm. I just don't usually use it.
I chose to use the harmonies that were the most successful in my tests. All of those measurements are for barrel lengthens of 65-69cm. For much shorter barrels I'm using different harmonie.
My tubes are costume made to each barrel. I don't sell standard length tubes...
Guy.

Even though I'm a pistol shooter, I'm thoroughly enjoying this thread.

Bryan996 wrote:Kevin - I'm still quite new to this so forgive me for asking (and its off topic) but isn't the best crown position decided on were the barrel slugs at the tightest?

cheers Bryan

Bryan:

I agree that RF barrels perform best with some measure of taper in them, tapering towards the muzzle. Slugging IMHO provides confirmation of proper lapping only. Crown position is another matter, and as I mentioned is critical for great performance throughout a barrels lifespan. I think it has nothing to do with tightness and everything to do with where the bullet exits in the vibration cycle.

I am reluctant to share much on this subject because of the controversial nature of it, and the fact that I have only hard performance evidence to base an opinion on....but here goes.

I don't believe that there are multiple nodes along a barrels length during the firing cycle. I believe the barrel vibrates as a fixed cantilever, and the "nodes" we seek are actually the farthest points in the cycle, as the muzzle slows, stops, and returns in the opposite direction. Gravity ensures motion primarily in the vertical axis. I think the tune positions (either manipulated thru crown location, movement of mass or manipulation of length) are best when at the top of this vibration cycle because lower velocities would exit later, theoretically at a reduced exit angle. It explains why we see lots that shoot competitively even though their velocity variation shot to shot is great (and I have seen this on many occasions).

If there was no "positive compensation", and the muzzle was "stationary" we would see nothing but elliptical groups....that had some X and Y axis accuracy error, and additional y axis velocity error. This is just not the case, great lots shoot round groups of equal X and Y axis error.....so where did the velocity error go? And even the best lots have some velocity variation.

Okay .....flame suit on! LOL

Kev

Hi All

I agree, this is quite a good thread.

I would like to contribute to this thread, but I feeling a bit under the weather, and it makes concentration a bit of a chore. I am thoroughly enjoying reading all the great responses.

PRX came about because I figured that bars and tubes operate according rules when it comes to vibration. I used those rules as they apply to tubes to determine node position in a given tube and harmonic. Basically I felt there was a mathematical formula to tuning.

Hopefully I will feel a bit better later today or tomorrow and can be a bit more engaging. But for right now I have a little experiment you can perform if you happen to have a spare barrel laying around. I want you measure the barrel and multiply that length by .224. Now measure back from either end and mark that length. Pick the barrel up with your thumb and forefinger at that mark so it is suspended. Now tap on the barrel lightly with a drill bit, screwdriver, small brass hammer. You should hear a clear distinct tone. Now move an inch so above and below the mark and tap again, the tone should be muted. Where you got the clear tone is a node. Math found the node because all beams will react the same, round, hollow, or even irregular shaped.

We shoot thru tubes, and there is a specific set of rules that govern them as well, and that is where I concentrated in coming up with PRX.

Gonna quit for right now and try to get a nap in. Hopefully I will feel a bit better and can more clearly discuss about tuning.

This is a great thread

Tony

Guy- Thanks for chipping in and I hope I didn’t offend you. I do understand that all your tuners are handmade for each barrel and each one will be a slightly different length. My comment was more directed towards the question of the different harmonies used for each tube length. I genuinely don’t understand how there can be multiple harmonies going on, but I’ll come back to that in a moment.

Kev – I agree with you about the fixed cantilever, that’s a very similar hypothesis to my horizontal pendulum, and I too believe that movement of mass and/or manipulation of length creates the results.

Tony – Thanks for joining the conversation and I hope you feel better soon. I have a few questions with your prx theory and hopefully you can set me straight!

Firstly, all the reading I’ve done on standing waves in a tube relate to air movement in a musical instrument, how does this relate to a round travelling down a barrel at the speed of sound? Exactly what waves are we tuning (vibration, air pressure, etc)?

It took me a while to work out that your maths isn’t trying to work out the quarter wave length of the barrel but instead calculate the NEW quarter wave length that would put the last node inside the tube to correspond with the muzzle(we know that standing waves in a tube with a closed end always have an odd number of harmonies with the open end always having the anti-node, that’s proven physics).

As I’ve said before I don’t understand how there can be multiple harmonies going on in the barrel. A tuning fork will always ring with the same note no matter how hard you hit it, so how can there be multiple harmonies in a barrel? And also how do you decide which harmony is the one to use? It must be an odd number but why can’t it be 17 or even 1327? And how does a moveable weight, like the one Guy has on his tuner, change things and why does it need to be moved to find the tune? Your maths only relates to tube length?

And finally if every round, regardless of speed, leaves the barrel at a node point why do we not see a different POI? Higher for the faster rounds and lower for the slower rounds? The only explanation I can come up with is that when it’s in tune (for a fixed distance) a slower round leaves the barrel at a higher elevation than a faster round, and only the recoil path would really fit that model.

Thanks Bryan

Just to chip back in with my original question as Bryan has hinted at it above - if you can tune or de-tune a barrel by moving a weight forwards or backwards a couple of thousandths of an inch at a time, how will I know how much of an effect the weight and placement of my foresight is having?

And what happens when I add weight to the foresight using sight raisers? If there a formula for working out how far down the tube to place my foresight based on it's weight?

Kind regards,
Lee

kevin nevius wrote:Good morning Mark:

I certainly appreciate your approach, and I meant no disrespect in the previous post. I have always appreciated your posts.

Kevin, absolutely none taken. Your experience, based on your testing and skill level, is invaluable and interesting. I'm curious, if you had two barrels of nearly identical dimensions, would your tuning method of trimming back the muzzle always produce the same length for a given ammo?

If my velocity measurements in a test a few years ago were accurate, the vertical measured at 100 was smaller than what gravity would produce given the velocity spread so there had to be compensation. (Calfee's node theory disproven). Geoff's vibration analysis, excellent work, proved the same in a better lab setting. If PRX is putting the muzzle at a node and compensation exists, it would seem to be sub-optimal.

To my simple way of thinking, for any given barrel length added tuner mass or length would be nearly interchangeable (equal moment arms if I remember my physics). But Friday at work I thought I understood how we should perform an optimization, yet two of the Engineers clearly weren't in sync so I kept asking questions until it finally got through my thick skull. What if there is more to this wave tuning theory than I currently appreciate. When I add a second weight to my BeeStings the length doesn't change, but the tune does. Does PRX predict this? Could it explain the narrow tunes that seem to only work for one ammo lot and the broad tunes that work for several? Perhaps the broad tunes can tolerate being shot out of the stock or moving from the bench to prone. Maybe PRX gets us close to one of those broad tunes?

I guess I need to drag out several rifles and do the math to see where they land.

There seems to be more to ammo quality than just the ES and SD from my tests. I was not shooting well in today's 1600, to much kayaking and not enough prone practice, but I decided to try some of the X-Act left over from the test in the 54.30. What's not to like with this vertical? Maybe it was luck, but since it is my any rifle I have no reason to hang a tuner.

Mark

Hi All

I just spent the last hour trying to answer some of your questions and when I went to submit, it kicked me off and I lost everything. I'm too tired to try and do it again, so Ill do it again tomorrow

Tony

Shifty wrote:Just to chip back in with my original question as Bryan has hinted at it above - if you can tune or de-tune a barrel by moving a weight forwards or backwards a couple of thousandths of an inch at a time, how will I know how much of an effect the weight and placement of my foresight is having?

And what happens when I add weight to the foresight using sight raisers? If there a formula for working out how far down the tube to place my foresight based on it's weight?

Kind regards,
Lee

Hi Lee:

In my opinion, yes - the foresight definitely effects tune. Any mass movement, addition or subtraction will effect overall performance. I test with everything in place and documented so I can repeat it. Most tube assemblies now offer dovetails opposed so that the foresight can be hung in the same longitudinal position - under the line of sight for anysight use (handy for testing with a scope too).

The additional mass of riser blocks would (for me) mandate re-testing. I would think that would certainly effect your non-block test results. Additionally, I know of no formula for calculating any mass / distance equivalents to simplify the process (sorry).

I use tube sight mounting blocks that are indexed within a thousandth or two (I use the forward edge for front sight location) - which is plenty accurate for testing repeatability.

Oh, and just an FYI.......I test in full tuner revolutions (of .025"). For me at least, I can't quantify the effects of a .001" click on paper (or even a half revolution for that matter at .0125"). I know some well respected shooters who say they can, but that's way too fine for me. I am OCD, but not that bad (yet!).

In my mind, the mass of the crud and moisture that accumulates in the extension equates to a few clicks, so I have resisted the urge to get that fine with it. Just me opinion.

All the best,

kev

Turns out Dr Geoffrey Kolbe has already done the maths and the hard work on muzzle angle for positive compensation:

http://www.geoffrey-kolbe.com/articles/ ... barrel.htm

I quote;

"The influential American rimfire gunsmith Bill Calfee, in an article written for Precision Shooting Magazine ("I'm Feeling Those Good Vibrations AGAIN!" Vol. 52, No. 11, March 2005) presented a rather novel view on how barrels vibrate, and also expressed his belief that for best accuracy, barrels should be tuned so that the muzzle is "stopped" and there is no change in muzzle angle, or position, as the bullet is launched. It should be noted that Calfee's theories have absolutely no basis in fact and are mathematically untenable. But that does not stop it being the most quoted work in the popular press on barrel vibrations and the tuning of barrels."

"It has been shown that the launch time of the bullet from the barrel, with reference to the transverse vibrations in the barrel, does vary with muzzle velocity, and this rate has been measured for Eley Tenex .22 rimfire ammunition in a 26 inch barrel. The proposition that positive compensation might be achieved by "tuning" a barrel, such that the muzzle angle is changing with time in a beneficial way at bullet launch, is thus a valid one.........When the barrel is tuned for complete positive compensation, no further improvement is possible."

In the test Dr Kolbe used a 200g barrel weight so I've emailed him asking why he used that amount, and also why do results change when winding the tuner weight out? Also looking at the results he acheived the perfect speed of the barrel by moving the vibrations back from a negative downward movement into a positive upward movement by lengthening the wavelength of the vibrations, the upward speed is the gradient of the graph and it looks like a coincidence that that part of barrel movement is the right speed. Adding weight didnt change the amplitude of the vibrations, only the wavelength.

Guy, have you tried testing two tuners of identical mass but differing lengths on one barrel? I'd be interested in those results. Also have you tested after tuning and then moving the foresight forwards and backwards?

thanks

Bryan,
The reason I made my tubes to be about 220gr,are the experiments I have made together with Dr. Kolbe.
We have found out,that much heavier mass doesn't allow us to get positive compensation.
I haven't try 2 identical weights,with different length tubes on the same barrel. I have tried my long tube, and short tube on the same barrel(weight difference is about 20gr). results,were about the same,considering both tubes were calculated by PRX. Tuner setting was different.
Changing the front sight weight or moving it,will definitely change the tuning.
I totally agree with Kevin,about everything he wrote in his post.
Guy.

Thanks for the reply Guy,

If you've experimented with Dr Kolbe why do you still use the PRX formula when Dr Kolbe has effectively disproved it? (PRX saying that the muzzle should be still and Dr Kolbe saying it should be moving).

The results you have acheived with long vs short tube could probably be due to the fact that you're using tubes that are a similar weight to Dr Kolbe's test at 200 grams. I am still intrigued as to why moving the tuner weight effects the results, maybe its changing the amplitude of the vibrations to create those that are ideal?

thanks

Bryan,
I don't think that Tony ever said that the muzzle should be still.In my opinion,the muzzle can never be still...
I use PRX because it works! I think that PRX+ tuner is even better. I use both methods to tune. It works for me,and for many international high level shooters.Moving the tuner weight changes the way the barrel vibrates,that's the reason why moving the front sight,changes tuning.
Guy.

Ok, Lets try this again

You are correct that much of the information relating to the harmonics of a tube that is closed on one end and open at the other refers to musical instruments. But any time you have gasses passing thru a tube, be it super sonic or subsonic, harmonics waves will form.

What we are doing is tuning the bore of the barrel, not the barrel as a bar.

You are also correct in that the QW of any harmonic is the key to tuning. Under normal circumstances we want the bullet to exit at a node, which would be one QW back from the harmonic value, IE 8th QW for the 9th Harmonic. So if we were to divide our barrel by 8 for the 9th Harmonic, we would get a length that is equal the QW necessary to put the muzzle at the 8th QW with the tuner, bloop tube making up the distance needed to complete the 9th, with the distance from the muzzle to the end of the tuner equal to the QW distance.

Pick a harmonic, subtract one, divide the barrel by that number, multiply by the harmonic number, subtract your original barrel length, and you are left with the length of tuner you need to tune the barrel. There is another step, but for this explanation, it can wait.

Lets wrap this portion up. More to follow

Tony

I think it is important to note that the node and the anti-node terms used with this form of tuning refer periods of highest pressure and greatest movement of the gasses is the anti-node, and the period of least pressure and least movement of gasses is a node. It does not refer to the actual movement of the barrel during its mechanical vibration.

Thanks for that explanation Tony, since I first heard of PRX I've been looking for a rational explanation of the phenomenon and what you just posted corresponds pretty much to what I'd concluded (with reservations).

With a tube of the correct length, a standing (acoustic/pressure) wave might be set up such that a "node" would be set up at the muzzle - this has two possible benefits.
1. As the bullet exits the pressure behind the bullet stays high for longer than it would - normally the pressure behind the bullet would drop from high to atmospheric very sharply and my feeling is that a sharp transition like that can't be good for bullet stability. The node is a high pressure point, the anti-node is the low pressure region. For the longest PRX tube there will be nodes at the bolt face and the muzzle and anti-nodes halfway down the barrel and at the open end of the tube.

2. At the node the particle velocity of the gasses behind the bullet as it exits will be low - meaning that the high pressure gasses will exert less force on the bullet as they pass it, causing less "tip off" of the bullet.

My reservations are that the bullet is traveling close to the speed of sound for a good portion of its travel down the bore and as it leaves the barrel - and in the time it takes to set up the standing wave the bullet is out of the tube and on its way to the target...

That said, I've adjusted the length of my tuner tube to a PRX harmonic (~102mm) as well as tuning the position of the weight and just had a cracking week at out National Championships.

Ken.

Bryan996 wrote:As I’ve said before I don’t understand how there can be multiple harmonies going on in the barrel. A tuning fork will always ring with the same note no matter how hard you hit it, so how can there be multiple harmonies in a barrel?

Hi Bryan, when you excite a bar or string with a sharp (transient) stimulus all the possible harmonics will be present but most will die out very quickly. The lowest harmonics which contain the most energy will ring on for the longest giving it a "timbre". If this were not the case then all plucked/struck instruments (guitars, harpsichords, piano, tubular bells) would sound the same - like sine waves with no harmonics present.

One of my favourite examples is a Fender Rhodes piano where a cantilevered bar (tine bar) is struck by a hammer - its frequency is tuned by moving a small weight along the bar and its timbre is altered by adjusting the bolts that attach the bar to the frame - like adjusting the tension on your bedding bolts...

Ken.