Tuners some info.

[Gene Beggs]

George, I sure,,

,,hijacked this thread; didn't I? But you'll have to admit I kept it on subject; huh?

Gene Beggs

 

[Bob Kingsbury]

Pacil

Your barrel temp seems quite reasonable,but I have to ask. If you began
shooting at say 65 degrees with your tuner set for that, what happens to the tune when barrel temp rises to 90. Are you now out of tune, and does that agree with what works

 

[K Hope]

Keith

If there is only minimal change of Total pressure from Atmospheric pressure does that not tell us it is Temperature and powder geometry that are the most significant factors in determining peak pressure.

Ken

 

[Gene Beggs]

Gene...Vibration of a barrel is influenced by the distance from the node out to the c. of g. of the weight of barrel swinging about this node, plus the weight of the tuner, pivoting about this node. In other words this weight of barrel and tuner creates a moment about the node. The moment is simply the weight multiplied by the distance from the node. It's these distances or lengths of barrel that are increased by a temperature rise. Of course a temperature rise in air means also a temperature rise in barrel.

(GB) Yes. All true.

So, your finding that the tuner must be moved in slightly to accommodate a rise in air (and barrel) temperature makes sense. You are simply keeping the moment about the node the same. Unless you use an extremely fine thread on the tuner I'm having trouble making the numbers work out but the principle makes sense to me.

(GB) Pacecil, I use 28 tpi which of course moves the tuner .0360 per revolution.

What may be happening is that as air temperature rises there is a slightly higher rise in barrel temperature because of lower heat transfer to the warmer air. I suggest this may be the mechanism that controls this "tuning" of a barrel rather than the properties of the air ahead of the bullet.

(GB) Could be, but I don't think so.



Pacecil, my comments are in bold preceeded by (GB) in your post above. Seemed easier that way. Hope this helps.

Later

Gene Beggs

 

[geo.ulrich]

Gene, i'm glad you did i got the answer i needed on your post#123 thanks. the problem as i see it is the difference between people giving nothing but theories on this and actually shooting and proving there theories. to quote jackie until you step up and shoot in the competitive arena all the talk is useless. george

 

[Gene Beggs]

Gene, i'm glad you did i got the answer i needed on your post#123 thanks. the problem as i see it is the difference between people giving nothing but theories on this and actually shooting and proving there theories. to quote jackie until you step up and shoot in the competitive arena all the talk is useless. george

Thank you George. It's been interesting; hasn't it?

Gene Beggs

 

[mks]

If there is only minimal change of Total pressure from Atmospheric pressure does that not tell us it is Temperature and powder geometry that are the most significant factors in determining peak pressure.

Ken

...different time of exit relative to the harmonics behavior.

I think you and Vibe hit the nail on the head. The predicted 0.006" growth of the barrel per 40 F change doesn't jibe with Gene's one turn (0.036" of tuner movement) over the same temperature change (George's measurements of 0.030" over 50.6 F also don't provide agreement). Moving the tuner in compensates mostly for the decrease in barrel exit time of the bullet. Increased barrel temperature decreases quenching of the charge, which increases MV and decreases exit time. Moving the tuner in increases the frequency of barrel vibrations to keep bullets with varying exit times leaving the barrel at the same range of points on the muzzle angle curve.

Cheers,
Keith

 

[Gene Beggs]

I think you and Vibe hit the nail on the head. The predicted 0.006" growth of the barrel per 40 F change doesn't jibe with Gene's one turn (0.036" of tuner movement) over the same temperature change (George's measurements of 0.030" over 50.6 F also don't provide agreement). Moving the tuner in compensates mostly for the decrease in barrel exit time of the bullet. Increased barrel temperature decreases quenching of the charge, which increases MV and decreases exit time. Moving the tuner in increases the frequency of barrel vibrations to keep bullets with varying exit times leaving the barrel at the same range of points on the muzzle angle curve.

Cheers,
Keith

Keith, you, Vibe and certain others feel it is changes in barrel and powder temperature that is responsible for taking our rifles out of tune and I can understand why you would suspect that but I am quite sure that is not the case. Let me explain.

First let me point out that I have been pursuing this 100, 200 and 300 yard group shooting for over 22 years in actual competition at ranges all over the country. I have been searching for the answers to this tune thing hot and heavy and it only took me about twenty years to figure it out. And I firmly believe I have finally got it figured out and results on the firing line in actual competition bear that out.

Oh,,, I don't shoot very well and you don't normally find my name very high on the match results because I spend too much time experimenting, building Wind Probes etc., instead of practicing, but my rifles shoot! And I can keep them in tune using only my tuner. Winning is just not that important to me. I get my satisfaction from unlocking nature's secrets and helping others. It tickles me to death when someone I have trained wins! Three good examples of this are Bryn Borras, Rod Brown and Matt Guthrie. But back to our discussion,,

Keith, if it was only the temperature of the barrel and ammunition that was responsible for taking our rifles out of tune, we could control that with coolant jackets in the form of wet towels on the barrel, insulated containers etc., but that is not the case.

For some time, there were a good number of group shooters using barrel coolers that circulated ice water, alcohol etc., thru their barrels between relays and since we frequently fire only six to eight rounds in each match, the barrels were being kept plenty cool. The rifles still went out of tune!

Today, you rarely see a barrel cooler except maybe a wet towel draped over it between relays, so I guess keeping the barrels cool made no difference or all the winners would still be doing it. But tuners? Now that's a different story. They work! And more and more shooters are discovering that. Even ol' Francis! Imagine that!

Later

Gene Beggs

 

[alinwa]

Trust me. It's amazing how much you have learned about tuners since I started using one of yours. There was a time when you knew nothing, you were a self-promoter, I had to teach you about tuners.
Okay, tongue in cheek. Don't everyone jump me.

FffbfFFRranscCsisSSS!!!!!!!

You've got a GIFT man..... USE it, don't ABUSE it......

BITE'cher tongue!!

LOL

al

 

[Gene Beggs]

Trust me. It's amazing how much you have learned about tuners since I started using one of yours. There was a time when you knew nothing, you were a self-promoter, I had to teach you about tuners.
Okay, tongue in cheek. Don't everyone jump me.

Francis, I love your sense of humor!

Gene

 

[mks]

For some time, there were a good number of group shooters using barrel coolers that circulated ice water, alcohol etc., thru their barrels between relays and since we frequently fire only six to eight rounds in each match, the barrels were being kept plenty cool. The rifles still went out of tune!

Gene,
You know a lot more about what has been tried than I do, but I wonder if anyone has run tests with truly constant barrel temperature shot to shot, as in plus/minus a degree or two. The evaporative methods you mention cool the barrel down to a range of temperatures around ambient, warmer if you apply them for a short time, and colder for a long time. And as ambient temperature changes, so does the range of temperature after cooling. Measuring barrel temperature with a pyrometer last season was a real eye-opener. In competition, uncooled barrels follow ambient temperature surprisingly closely. (Fan-cooled barrels follow ambient temperature very closely.) If barrel temperature is in lock step with ambient temperature, it is difficult to identify which is the actual cause of detuning.

It sure would be interesting to try a true constant temperature bath surrounding a barrel. Shoot it in different ambient temperatures, and then we would know.

Cheers,
Keith

PS. I have nothing against tuners. My next rifle will have a tuner on it.

 

[alinwa]

In my time of playing with tuners I've never noticed my tune changing as the barrel heated up...... Anyone else???

Am I missing something?


al

 

[Gene Beggs]

Hal, after reviewing one of your posts, I thought I should clear something up and that is,,

Your tuners are 'beyond-the-muzzle devices' and you are correct when you say,

I believe the weight of the tuner is VERY important. I'm not saying that any particular weight is the key weight, just that heavier tuners (within reason) require less adjustment, less often. I also feel that just as strongly about the majority of the tuner weight being beyond the muzzle as opposed to being behind it.

During discussions with Bill Calfee, it was obvious, he was talking only about beyond-the-muzzle tuners; he even began refering to his tuners as "Muzzle Devices." And I think that is a better description.

On the other hand, the behind-the-muzzle tuner is just that; a "Tuner." It works by raising and lowering the barrel's vibration frequency and within reason, weight is unimportant but the distance moved fore and aft on the barrel IS.

I shoot only 10.5 pound Sporters and Light Varmint rifles in short-range group competion. Beyond-the-muzzle tuners/devices are impractical for my use because of weight restrictions. Six to eight ounces added beyond the muzzle also makes the rifle nose heavy.

Later,

Gene Beggs

 

[crb]

Maybe in the future a heavy 'btm' tuner will be one of the things that distinguishes a HV rifle from a LV rifle and maybe then the HV gun will show some grouping superiority over the LV.

 

[Hal D.]

Hal, after reviewing one of your posts, I thought I should clear something up and that is,,

Your tuners are 'beyond-the-muzzle devices' and you are correct when you say,




During discussions with Bill Calfee, it was obvious, he was talking only about beyond-the-muzzle tuners; he even began refering to his tuners as "Muzzle Devices." And I think that is a better description.

On the other hand, the behind-the-muzzle tuner is just that; a "Tuner." It works by raising and lowering the barrel's vibration frequency and within reason, weight is unimportant but the distance moved fore and aft on the barrel IS.

I shoot only 10.5 pound Sporters and Light Varmint rifles in short-range group competion. Beyond-the-muzzle tuners/devices are impractical for my use because of weight restrictions. Six to eight ounces added beyond the muzzle also makes the rifle nose heavy.

Later,

Gene Beggs

I've got a couple sporters myself Gene. And while it is a bit more difficult to make a balanced rifle with a heavier tuner (mine are 5.6 - 5.7 ozs), it can be done. My setup utilizes a special contour that I came up with just for 10.5lb guns. My rifles balance very nicely with around 5ozs of weight added to the butt, and an LCS scope. The barrel's weigh in at just under 5 lbs, with the tuners installed. I will admit that your tuners set up well for the average shooter that doesn't have the ability to play with these weight issues, like some of us do.

 

[Gene Beggs]

Al, I hate to tell you this, but,,,,

I've always understood that the best area to shoot falls right below and behind the peak of a wave, where the barrel has stopped and is starting back down. POI is descending while velocity is rising.

al

,,,your statement above is wrong.

I have been studying this for days. I have reviewed,

1. Vaughn's book, "Rifle Accuracy Facts" (RAF)

2. Ratigan's "Extreme Rifle Accuracy" (ERA)

3. Varmint Al's website.

On page 86, second paragraph of RAF, Vaughn states,

"The best place to shoot is just past a positive peak on the curve."

(GB) In my opinion, that can't be right. I'll explain later.


On page 128 of ERA, Ratigan states,

"You want to tune your rifle so the average bullet exits the muzzle just after the positive peak, when the barrel just starts to go back down. Minor changes in velocity will be compensated for. Higher velocity, lower release from muzzle, lower velocity, higher release."

(GB) Huh? Say what? No, that isn't right! The best place for the average bullet to exit is just BEFORE the positive peak while the muzzle is still rising. Faster bullets that reach the muzzle sooner will be released at a slightly lower angle than slower bullets which will be launched at a higher angle thereby compensating for small variations in muzzle velocity. Varmint Al says the same thing.

You want your rifle tuned so that the average bullet exits just BEFORE a positive peak or just AFTER a negative. Think about it; you will see what I mean.

Of course, I realize all this is academic. In actual conditions in the real world, the rifle will tell you when it's in tune but I thought you would be interested in hearing this.

Later

Gene Beggs

 

[Gene Beggs]

Maybe in the future a heavy 'btm' tuner will be one of the things that distinguishes a HV rifle from a LV rifle and maybe then the HV gun will show some grouping superiority over the LV.

Good point Ray! I'll bet you're right.

We are making good progress; aren't we?

Later

Gene Beggs

 

[Gene Beggs]

Al you and Keith are probably right about this. Dr. Jack Jackson always tried to get this thru my thick skull but I never did quite understand. And you know, it really doesn't matter because the barrel will tell me when it is in tune; it's smarter than I am.

See my post number 144.

Gene Beggs

 

[Gene Beggs]

I got it from Borden....

Who worked w/Jackson and Vaughn et al.... I remember calling Jim in '97 or so and asking "but-but-but.... if the barrel's FALLING and the faster bullet gets there SOONER then how can it be that....???? al

(GB) That's my point. See my post # 144 and #161.

Gene Beggs

 

[Boyd Allen]

On the rise, where the curve flattens out, just before the peak, compensates by letting the faster dropping slower rounds exit at a higher angle than the flatter trajectoried faster ones that exit at a lower angle. Varmint Al's graphs are a great learning aid, and unique in my experience. Learning new stuff is fun!