Vibration Experiment of a Tuned Barrel

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Varmint Al

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Vibration Experiment of a Tuned Barrel
Here are the results of an excellent experiment on barrel vibration. Geoffery Kolbe, (Border Barrels in the UK) instrumented a barrel so that he could measure the change if angle at the muzzle. The angle rate of change is affected by a muzzle mass. With small variations of the bullet's muzzle velocity he was able to show positive compensation to eliminate vertical stringing at a given target distance. Click on the link to view the experiment results.

http://www.border-barrels.com/articles/rimfire_accuracy/tuning_a_barrel.htm

Good Hunting... from Varmint Al
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So now I know why my experiment with an oscilloscope and vibration sensor on my Win52 muzzle didn't pick the tuner sweet spot like I thought it would. I picked the peak, or null spot for the tuner setting, when I should have been looking for the positive compensation, or rising muzzle setting. Musta been the right place, but the wrong time, as Dr John said.
 
Quite interesting. Al do you have any thoughts on the ideal spread in MV from fast to slow on any two lots of ammo that are ideal to validate a tuned barrel? Also is there any thought as to wether there exists optimum MV range for tuning purposes that may not be the same for shooting matches in variable weather conditions? Thanks for any input.
 
way back to partial differential equations

Excellent work. I have been experimenting with a FEM made up of a cylindical sections and computed natural freq, but not to the extent of Al Harrel. My Win 52 has the same problem, but my trial and error would have taken 15 yrs. Really the key is the peak of the history curve where the partial derivative is zero. So how do we get there, obviously a slower projectile but mass of the tuner? Both. Maybe the natural freq would be a clue. i've got to think about that. I knew Al was getting close. This is a significant effort and especially since the travel time of the 22 RF allows many vibrations. Thanks Al Harrel been reading your page for many years.
J M (Mike) Hillman PE & LS
Cullman, AL :D

PS In my humble opinion the length of the barrel is only 17" for the nodal analysis BUT the issue of internal ballistics is 26". A dichotomy of sorts.
 
Mike

Is there any chance we could have that in plain language please. Like the man says " explain it like you would to a 6 year old".:eek:
 
Having followed all that I can find on barrel vibrations and seeing the results of tuners in use, its clear they can be effective.
I do have at least 2 guns where the barrel vibrations are quite audible. One is a rail gun and the other, a wood stocked
6.5 x 47 with 28 inch barrel. Questioning this, I placed a 3 ft piece of 3/8 drill rod in a vise clamped between 2 pieces of wood.
Following the initial excitement vertically, which faded out, a second wave occured and it took off again. There was also a third.
During any of these waves, there was also a horizontal motion. I suspect that all barrels are really that unstable. My question
however is, how do we know, there aren't outside sounds and vibrations that are affecting barrels before the pressure wave
begins. If a barrel is already in motion, between shots, wouldn't it be better to find a way to deaden the barrel while at rest.
Gene Buckys demonstrated to me how his barrel was actually dead.
If these barrels are in fact tuning forks, there are at any match , similiar barrels
osscilating at close to the same frequencys and able to excite other barrels.
 
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Thanks for posting the link, Al. This is really good work, with an ingenious way of measuring muzzle angle.

Thanks,
Keith
 
Bob,
I have used Sims Deresonators to deaden both of my short rang benchrest (6PPC) barrels that are fitted with tuners. They are called by another name these days, on their web site. Why don't you pick one up and give it a try. They are made of the gummyest rubber imaginable and seem to do an excellent job of dampening barrel vibrations. If you tap a free floated barrel that has one in place on it, instead of the usual "ting", you get more like a ""tunk". I have placed mine at the back of the tuner threads that are cut on the barrel, which extend 2" from the muzzle. If you look at the article about Joe Friedrich's rifles (rimfire, record setting), in Guns of the Week, on Accurateshooter.com, you will see one in the center of his rimfire barrel. He tests his in various positions. I believe that he uses 1/2" moves when testing. Back when the Deresonators had first come out, they only came with a 5/8" hole in the center. Wanting to do some experimenting on my bench rifle, I called and suggested that they consider offering one for larger diameter barrels. They did, and eventually sent me two identical prototypes, that I still have. Friends of mine, that have bought and tried them on various rifles have found that on some rifles they make a noticeable improvement in accuracy, and on others there is no change. These are all CF rifles that do not have tuners. My take on this is that if a rifle has a vibration related problem, then it will help, and if not possibly not. As to your free floated rod, I think that while it may give some illumination as to wave form and node locations, that the way that a barrel acts is different in how the energy that makes it vibrate is imparted. Starting in the sagged (gravity) position, I believe that the pressure behind the bullet stiffens the barrel, much like how a hose acts when you turn on the water, and since the deflection is downward, the straightening motion is primarily upward. This force is added to that caused by a rifle rotating around its center of mass, as it recoils, which also happens primarily in the vertical plane. Robert Vaughn is of course the source of my thought on this idea.
Boyd
 
I believe Friedrich has since ceased using those. They are inexpensive enough to test and see if they work for your setup though.
 
I just got off the phone with Joe, and he still is using them. He says that whatever difference they make is very subtle.
 
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