finding an "accuracy node".

[Steve Blair]

Almost all pressure guns use piezo transducers. What makes you think the one in your example uses a strain gauge?

 

[BoydAllen]

Catshooter,
I think that it is a grievous and flagrant violation of the unwritten rules of theoretical discussions that are based on imaginings to introduce hard data. How dare you? ;-)

Thanks, I learned something.
Boyd
PS. Fro the rest, I choose a powder that fills the case at max pressure, pick a seating depth based on experience, run a series of single shot tests at .3-.5 gr. intervals, shooting over a chronograph and flags, on an easy wind day, and look for clustering near the top charge. I stop when I get a tight bolt lift, working with FL sized cases, and working with the middle charge weight of the most promising looking cluster, I start to experiment with seating depth. If my investigation takes me off of the lands, I pick a distance off and redo the powder test in a narrower range, before proceeding with off the lands experimentation. With a good rifle, I look at two shots, until I see something that looks interesting, and then test that load with more shots per group. If two look ugly, adding more will not fix it.

 

[Syncrowave]

SPClark and Longshooter70, thanks for those links. Very interesting thread, everyone.

 

[40X Guy]

Excellent thread everyone!

Frank

 

[CatShooter]

Almost all pressure guns use piezo transducers. What makes you think the one in your example uses a strain gauge?

My pressure gun uses a inertial Piezo electric generator, but there is a trend towards strain...

... "What makes you think the one in your example uses a strain gauge?"

Cuz, Dummy, the guy that did the work, said so!! I didn't get off the melon truck last week. I've been doing this stuff for since forever!!



Boyd... I truly apologize for introducing facts into the typical debate made up of suppositions, myths, and faerie tails. I will try to behave better in the future. :-[ :-[

 

[Raythemanroe]

Catshooter,
I think that it is a grievous and flagrant violation of the unwritten rules of theoretical discussions that are based on imaginings to introduce hard data. How dare you? ;-)

Thanks, I learned something.
Boyd
PS. Fro the rest, I choose a powder that fills the case at max pressure, pick a seating depth based on experience, run a series of single shot tests at .3-.5 gr. intervals, shooting over a chronograph and flags, on an easy wind day, and look for clustering near the top charge. I stop when I get a tight bolt lift, working with FL sized cases, and working with the middle charge weight of the most promising looking cluster, I start to experiment with seating depth. If my investigation takes me off of the lands, I pick a distance off and redo the powder test in a narrower range, before proceeding with off the lands experimentation. With a good rifle, I look at two shots, until I see something that looks interesting, and then test that load with more shots per group. If two look ugly, adding more will not fix it.

So you are a ladder tester? Would this be at 100y or 300y?

Ray

 

[jlow]

I think it is difficult to pressure data to proof or dis-proof whether there is a pressure wave bouncing back and forth – here is the reason.

What you are looking at when you see a pressure curve is the overall pressure which is read from a strain gauge probably located at the chamber. It does an excellent job of measuring overall pressure inside the chamber over time from the ignition of the powder.

Not so - the strain gauge reads ANY expansion of the metal - if there is an expansion from gas pressure, and an expansion wave moving through the area of the tape, it will show both on the graph.

Here is an interesting article on muzzles. One of the better shooting magazines (Rifle or P.S.) did a similar article using a bench rest rifle.

http://www.longrangehunting.com/articles/rifle-crown-1.php

Sorry for the slow response - you guys post past my bedtime! ;D

I agree that the strain gauge will read any expansion of the barrel, what I mean is you might not be able to see the signal causing the expansion at the crown it since it is likely much smaller than the large one showing the pressure change in the chamber. There is likely not ONE thing going on here but multiple and what the gauge is showing you is the overall picture but if you can magnify and change the scale of the display you will see those small ones superimposed on it in the background - that is the reason why these pressure curves are not smooth.

Thanks for the article! It is indeed a very interesting one but it address the condition of the crown but not the “flicking” of the crown cause by the pressure wave moving through it.

 

[BoydAllen]

Ray,
100, and it is not a classical ladder, but a variant that does a couple of things, including show me the maximum practical load for a particular barrel, for a particular set of components, at a given set of ambient conditions. In just a few shots I get a lot of information. Typically, I can arrive at a good load pretty quickly, while loading at the range.
Boyd

 

[Steve Blair]

Almost all pressure guns use piezo transducers. What makes you think the one in your example uses a strain gauge?

My pressure gun uses a inertial Piezo electric generator, but there is a trend towards strain...

... "What makes you think the one in your example uses a strain gauge?"

Cuz, Dummy, the guy that did the work, said so!! I didn't get off the melon truck last week. I've been doing this stuff for since forever!!

[br]
Nice response there, pu$$y. : [br]
There is no "trend" toward a strain gauge that a piezo transducer exhibits. They are installed in a heavy portion of the barrel, over the chamber, and would have almost zero opportunity to prove or disprove the presence of the predicted wave. I am not defending or promoting Long's theory but what you have presented does not address it. [br]
If you were to conduct a test with several strain gauges, arrayed at intervals along the barrel, sample them at a reasonable frequency, and they were to show no sign of the predicted wave, you would have something. As it is, you have irrelevant data that does not address the problem.

 

[Jay Christopherson]

If you were to conduct a test with several strain gauges, arrayed at intervals along he barrel, sample them at a reasonable frequency, and they were to show no sign of the predicted wave, you would have something. As it is, you have irrelevant data that does not address the problem.

That's almost the exact test that Chris proposes(d) to use to validate the theory, along with the use of acoustic microphones. As far as I am aware, he has not actually conducted the test, although I'm sure he would be highly interested in the results if someone were to do so. He has very little personal time in recent years to conduct the test himself...

 

[Raythemanroe]

I would suspect a wave would be much slower then an oscillation. Then would it be fast enough to have a major effect on accuracy? How many waves would there be before a bullet left the barrel? When your working up a load are you trying to tune with one wave or multiple waves? I ask this because when it is theory and not a measured wave how much relevance does it have other then a preferred method of tuning?


Ray

 

[CatShooter]

I think it is difficult to pressure data to proof or dis-proof whether there is a pressure wave bouncing back and forth – here is the reason.

What you are looking at when you see a pressure curve is the overall pressure which is read from a strain gauge probably located at the chamber. It does an excellent job of measuring overall pressure inside the chamber over time from the ignition of the powder.

Not so - the strain gauge reads ANY expansion of the metal - if there is an expansion from gas pressure, and an expansion wave moving through the area of the tape, it will show both on the graph.

Here is an interesting article on muzzles. One of the better shooting magazines (Rifle or P.S.) did a similar article using a bench rest rifle.

http://www.longrangehunting.com/articles/rifle-crown-1.php

Sorry for the slow response - you guys post past my bedtime! ;D

I agree that the strain gauge will read any expansion of the barrel, what I mean is you might not be able to see the signal causing the expansion at the crown it since it is likely much smaller than the large one showing the pressure change in the chamber. There is likely not ONE thing going on here but multiple and what the gauge is showing you is the overall picture but if you can magnify and change the scale of the display you will see those small ones superimposed on it in the background - that is the reason why these pressure curves are not smooth.

Thanks for the article! It is indeed a very interesting one but it address the condition of the crown but not the “flicking” of the crown cause by the pressure wave moving through it.

The problem with that is...

Any wave that traveled along the axis of the barrel as a "shock wave", would be traveling at just over 20,000 fps. Since the barrel is ~2 feet long, one round trip is 1/5,000 of a second - the bullet takes 1,5-ish milliseconds to reach the muzzle... so there should be 5 or 6 waves superimposed over the pressure trace as the barrel expands for each shock wave (or so the theory goes).

"If"... the wave is strong enough to make the bore "loose"at the muzzle, and it is the fifth or sixth reflection, then the first, second, third, etc reflections have to be a hellovalot stronger than the last wave that would effect the bullet on exit.

There is no way in hell that these waves could be lost in the electronic "noise".

Further, if such waves were running back and forth in a barrel with a bullet (backed with 55Kpsia of very hot gasses) traveling down it - every time the wave passed by the bullet, the expanded section of the barrel would let burning hot, high pressure gas to slip past the bullet... and that would cause melted copper to be blown forward of the bullet and settle on the cold bore. All of that would mean that - the bullet(s) could never leave the barrel the same way as the others, since this effect would be random, and - the barrel would have to be cleaned every two or three shots.

If you look at the physics and the mechanical elements of this.... it is impossible.

 

[CatShooter]

Almost all pressure guns use piezo transducers. What makes you think the one in your example uses a strain gauge?

My pressure gun uses a inertial Piezo electric generator, but there is a trend towards strain...

... "What makes you think the one in your example uses a strain gauge?"

Cuz, Dummy, the guy that did the work, said so!! I didn't get off the melon truck last week. I've been doing this stuff for since forever!!

[br]
Nice response there, pu$$y. : [br]
There is no "trend" toward a strain gauge that a piezo transducer exhibits. They are installed in a heavy portion of the barrel, over the chamber, and would have almost zero opportunity to prove or disprove the presence of the predicted wave. I am not defending or promoting Long's theory but what you have presented does not address it. [br]
If you were to conduct a test with several strain gauges, arrayed at intervals along he barrel, sample them at a reasonable frequency, and they were to show no sign of the predicted wave, you would have something. As it is, you have irrelevant data that does not address the problem.

Uh huh... sure

 

[seymour fish]

Steve, Agree, starting with puzzy, and continuing with "when sound wave travels, the medium in which it moves is subject to stresses and strains" . This from 'Scientific Design of Exhaust and Intake Systems" by Smith and Morrison. published 1962. Apparently Columbia has relaxed their admission standards. Seymour

 

[seymour fish]

Cat, please calculate the expected pressures of the reflected waves you mention, and the expected stresses and strains your calculations dictate should be found, and your notions of how these might better be detected. Attention to sampling rates and various transducers of more appropriate sensitivity is excellent guidance. Then report back. Seymour

 

[CatShooter]

Cat, please calculate the expected pressures of the reflected waves you mention, and the expected stresses and strains your calculations dictate should be found, and your notions of how these might better be detected. Attention to sampling rates and various transducers of more appropriate sensitivity is excellent guidance. Then report back. Seymour

And the salary you are offering is... ??

 

[dmoran]

Further, if such waves were running back and forth in a barrel with a bullet (backed with 55Kpsia of very hot gasses) traveling down it - every time the wave passed by the bullet, the expanded section of the barrel would let burning hot, high pressure gas to slip past the bullet... and that would cause melted copper to be blown forward of the bullet and settle on the cold bore. All of that would mean that - the bullet(s) could never leave the barrel the same way as the others, since this effect would be random, and - the barrel would have to be cleaned every two or three shots.

If you look at the physics and the mechanical elements of this.... it is impossible.

Why would it ?
I disagree and my input is the resultant reflected waves from the shock wave are a disruption of the barrel steel at the point of the reflected wave, but not as a total bore-expansion as your alluding.

Oscilloscope tests show very well barrel movement and disruption to the entire length of the barrel, both in front of the bullet and behind (before & after affects), as well as the exact of movement and bore expansion at the bullet, for the extent of its in-bore travel. The actual bore-expansion can be measured with an oscilloscope and can not be with a pressure sensor.

Personally I have never tested with an oscilloscope, but I have and use a strain gauge pressure trace system (RSI) since 2006, and I am a very firm believer in Optimal Barrel Times (OBT) and Chis Long's theory's. The trace software has the OBT parameters in it, and repeatedly to very high percentages, where I find optimal best accuracy, will line up directly or almost directly inline with the OBT markers, which proves the theory very well.

Donovan

 

[dmoran]

Cat, please calculate the expected pressures of the reflected waves you mention, and the expected stresses and strains your calculations dictate should be found, and your notions of how these might better be detected. Attention to sampling rates and various transducers of more appropriate sensitivity is excellent guidance. Then report back. Seymour

And the salary you are offering is... ??

Seymour fish - not asking for much are you !.!.!

Can I get in on this as well...... lol
It sounds expensive and a bit complicated, and might be a little over-whelming for Catshooter to do by his self.
That is of course dependent on your offered fee if it would even take place.

 

[GSPV]

If tune is all about a knot running up and down the barrel, how do tuners work? And, we know from experience that they do.

If tune is all about a knot running up and down the barrel, and open tube as in a suppressor, beyond the muzzle doesn't count, how does the Purdy Rx work for rimfires? And it does.

I don't have answers. But, I don't claim to.

 

[CatShooter]

"...where I find optimal best accuracy, will line up directly or almost directly inline with the OBT markers, which proves the theory very well.

Donovan

It may prove something, but it does NOT prove that there are axial shock waves reflecting back and forth in the barrel.