Author Topic: Another Harmonic Killer Test  (Read 1233 times)

sixshootertexan

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Another Harmonic Killer Test
« on: April 29, 2019, 07:36:38 PM »
I took the big brass weight off that I used for a harmonic dampener and going to try something different. I made 4 pieces that is shaped like my twin tubes and barrel configuration of my .308 rifle. Once fitted they look like a vent ribbed barrel shotgun. They have a set screw in them to hold them in place and help with the harmonics hopefully. If this does not work I got another idea I want to try.

 

There are 4 installed. You just can't see the one under the scope.




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rsterne

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Re: Another Harmonic Killer Test
« Reply #1 on: April 30, 2019, 07:12:39 AM »
Interesting idea.... I guess they push up on the barrel where installed, with the pressure adjustable with the setscrew?.... If the tube bends a different amount at different pressures, you may see a POI change.... JMO....

Bob
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sixshootertexan

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Re: Another Harmonic Killer Test
« Reply #2 on: April 30, 2019, 07:42:39 AM »
I sure there will be a POI change. Just hoping that the harmonics don't cause the blocks to move since they are not fastened to the tubes.
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rsterne

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Re: Another Harmonic Killer Test
« Reply #3 on: April 30, 2019, 12:22:43 PM »
Maybe leave them loose enough that they DO move.... If the accuracy improves at the location, lock them down there.... If it is worse, move them to the positions halfway in between and lock them down there....  ???

Bob
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steveoh

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Re: Another Harmonic Killer Test
« Reply #4 on: April 30, 2019, 04:07:54 PM »
I've found it fascinating to watch slow motion videos of big bore airguns firing and seeing barrels flex and bend in what might be described as a wave. After watching one of these videos I thought I'd like to wrap a barrel of my newest .257 with carbon fiber and stiffen that sucker up.
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Nvreloader

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Re: Another Harmonic Killer Test
« Reply #5 on: May 20, 2019, 07:13:39 AM »
Ricky

To find the harmonic node points of the bbl, you might want to try this trick,
make several "U" shape horseshoes, from paperclips, place them about 2" apart down the bbl's length,
these horseshoes must be able to freely move along the bbl's length.

Fire several shots with NOTHING touching/holding the bbl, including bbl bands, clean floating bbl etc,
after several shots you should see these "U" shaped weights migrating to certain spots along the bbl's length.

Where these horseshoes collect is a node point for that bbl and load etc.
Gives you a starting point unlike a SWAG etc.

This trick was shown to me by Wes Ugalde, the Ugalde series of TCU cases,
Wes made bbls with a Dog Knot on the bbl's ends for XP 100 pistols in all of his calibers,
22 thru 30 cals, and each one was tested this way to find the node points at the bbl's end,
within a bbl's taper/cal, and they were VERY accurate etc. 

Tia,
Don
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strever

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Re: Another Harmonic Killer Test
« Reply #6 on: May 20, 2019, 08:41:48 AM »
Don
what in the world is a barrel dog knot?
Dick

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rsterne

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Re: Another Harmonic Killer Test
« Reply #7 on: May 20, 2019, 12:39:03 PM »
A swelling (ie larger diameter portion) at the end of the barrel....

What I don't know is do you want to position any barrel support or barrel band at the node, or halfway between?.... Don ????

Bob
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Nvreloader

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Re: Another Harmonic Killer Test
« Reply #8 on: May 20, 2019, 02:05:04 PM »
Bob and Strever

When Wes made up his bbl's,
he would find the node point that was closest to the 15" max bbl length, per ISHMA rules,
depending on the bbl taper/weight and caliber and cut a Dog Knot on the end, large enough diameter,
where he placed the front sight, then check with his loads to see the results.

Wes always put the front sight right on the node middle, IIRR, there was approximately 1-1/2" of space,
so the Dog Knot could be moved either way, and or shortened up etc,
and according to WES, this was where the bbl centered on the imaginary center during the bbl fish tailing,
side to side and up and down etc, when firing etc.

The German 98 bbls were set up this way also, the steps in the bbl are node points etc.

Dog Knot = an enlarged diameter of bbl, where the front sight was placed,
the OLD pre 64 M-70 Winchesters, had a Dog Knot where the OEM rear sight was installed etc.

I shot the best groups ever with iron sights, with my 250-3000, XP/100, factory ammo, 5 shots = 9/16" @ 100 yds,
15" bbl and scoped now and still hunt with it to this day.

I would love to test this on an air gun, but I don't shoot bullets/slugs etc.

If you want to be controlling the bbl nodes,
once you find the node points, record the distances from the breech face,
place a insert/bbl band there, or all other node points and shoot, see the results for accuracy,
then place the insert/bbl band halfway between the node points and shoot,
you should see different results and then go from there.

Tia,
Don
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Alan

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Re: Another Harmonic Killer Test
« Reply #9 on: May 20, 2019, 02:53:27 PM »
While we're on the subject.... And based on my experience in bench rest (firearm) shooting....

I know the importance of barrel tuning, bedding, tensioning, whatever. But I get the impression that using "node tuning" (an air rifle) is more accurate than say putting the barrel under tension? Just answering this specific issue, leads to a myriad of other questions! Like....

Does anyone know what the size of the smallest "screamer" group shot during a sanctioned, airgun Field Trail? This said, even a lousy shooter, using lousy barrel, and everything else lousy, sooner or later, will prove Occam's Razor and shoot a screamer group. Which leads to the real subject. In a Field Trial scenario, will node tuning prove to be the winning strategy?

And lastly, what if we build an airgun with a one inch OD, solid stainless steel barrel. Will that airgun require barrel tuning?
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Nvreloader

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Re: Another Harmonic Killer Test
« Reply #10 on: May 20, 2019, 03:19:40 PM »
Alan

I don't have enough experience as for air guns, like you my experience comes from the PB field, etc.

I do know that the node effect on bbl's is real and can make a big difference in accuracy, ie,
Cris Long's OBT info relies on bbl nodes and QL and it works etc,
after seeing my 18" bbl'd, 284 Win pistol, 140 N Parts at 3100 fps+ and lots of -3" groups @ 300 yds,
with 15X rifle scope.

I tried getting QL to work with AG bbl nodes and I can't get the formulas to work for the low FPS reading etc.

I am hoping that I can get this Gauntlet's bbl POI shifting stopped,
and then I will try the node testing, with pellets to see the results etc.

Tia,
Don
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rsterne

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Re: Another Harmonic Killer Test
« Reply #11 on: May 20, 2019, 03:58:59 PM »
I don't think you can use the pressure related equations to calculate barrel vibrations in an AG.... However, they DO vibrate, and the thinner they are the more they move.... I have no idea if a 1" diameter steel barrel would still vibrate enough that tuning would make any difference or not....

Handloaders can tune their loads to the barrel.... Rimfire shooters use a muzzle mounted harmonic tuner to tune their barrel to the load, because they can't change the velocity.... AG shooters can do either, we can try different velocities to tune the pellet release point to the barrel, or tune the barrel to a specific pellet and velocity.... We can tune the barrel by using a harmonic tuner like a rimfire, or a sliding weight ala limbsaver…. OR we can tension the barrel (or sleeve it) to change the amplitude and frequency of the vibration.... I think that any of the methods may require a tweak with a change of pellet, pressure or velocity.... but in theory the tensioned or sleeved barrel, like the thicker barrel it is trying to emulate, should have a wider "sweet spot"....

We can purchase CF sleeves that are 30 mm (1-3/16") in diameter that will slide over a 20 mm sleeve, such as I use on my sleeved barrels now.... I can't imagine something that diameter would move at all....  8) …. Alternately, you can buy 28" LW untapered benchrest barrels up to 1.2" diameter or more, but they weigh up to 9 lbs, just for the barrel....

Bob
« Last Edit: May 20, 2019, 04:18:27 PM by rsterne »
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steveoh

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Re: Another Harmonic Killer Test
« Reply #12 on: May 20, 2019, 04:10:27 PM »
In Jujutsu weapons training, we use the Jo, a simple hardwood staff about 53" long. We are taught to find the sweet spot to grip by tapping the front edge on the mat with one hand, at the rear of the Jo. You slide your hand forward and backward and keep tapping. The wood rings when you find the sweet spot, and this is where you grip the Jo with your forward hand for many of the Jo techniques. I've fiddled around and struck inanimate objects with the Jo while holding at the sweet spot and not on the sweet spot. The sweet spot makes for a more solid feel that I think transmits more energy to the person or object you are smacking. Of course there is a sweet spot on either end. Perhaps this is something that could be done with a barrel, and mark those sweet spots.

Of course it could all be bunk.
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Alan

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Re: Another Harmonic Killer Test
« Reply #13 on: May 20, 2019, 04:21:36 PM »
When hand loading (powder guns) for accuracy, consistency is the real key. Once upon a time, I used to use a powder dropper when reloading, which allowed the addition of just ONE grain of powder to fall into the case! What's more, bullet weight was MUCH closer than what we're used to with respect to pellet-to-pellet weight. It is a darn wonder we can do what we do, all things considered.
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Nvreloader

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Re: Another Harmonic Killer Test
« Reply #14 on: May 20, 2019, 08:54:48 PM »
Bob
You are correct, QL will NOT work with AG's at this time.  >:(
HL can tune their bbl via using node points of the load data they are using,

I have never messed with most of the tricks you mention when using AG's,
but I would believe that when you change any item, ie: psi, pellet/bullet weights, bbl lengths,
which changes the bbl's movements, you may have to change other options to get the best results etc.

I have never messed with CF sleeves, looked several times but never found the proper I/S dia,
to fit any of the bbl's I have or use, this Gauntlet bbl may be the first I want to try,
if my next experiment I am working on don't work or stop this wet noodle bbl POI shifting etc.

Steveoh
You are way above my pay grade with the martial arts training,
we were taught, if the suspect went into that type of fighting stance,
you deployed your sidearm and could use it, if advanced on and felt threatened etc.
I do know that a simple hardwood staff about 53" long = Rod is very dangerous in the correct hands,
that know how to use it.

Alan
Yes, I have spent lots of hrs using a powder dropper, bringing loads up to the proper levels etc,
I went so far as adjusting/tuning my scales to read 1 kernal of powder when dropped on the pan,
the best item was a needle Super Glued into the scale pointers groove, to read to a very fine adjustment,
on the ladder scale.  You wouldn't believe how accurate you can get with just that trick alone.

When WES started using the Dog knots on his bbl's nodes,
he tried several other tricks, but none was as good as finding the nodes and Dog knot trick,
he had a large HD vise set outside on the range behind the shop,
he made a large square 3 sided x 6" long, thick square piece of lead, wall thickness was 3/4"+ thick,
it just fit the XP bbl'd actions he was using etc.

He would securely clamp the XP bbl'ed  action inside this lead sleeve, and tighten the whole works in the vise,
then he would take a lead hammer and hit the top of the action, after he placed the horseshoe loops on the  barrel,
every 1" or so, after several blows these rings would gather at/around the 15" length of the pre turned bbl,
I never seen any bbl that had more than 1 node spot in the 15" bb length, but I would believe that a 30" bbl would have 2-3 node spots.

Then he would remove all the rings but one, and repeat the process several times,
marking the exact spot where the ring stopped etc.

Then he would start turning the bbl to the dimensions needed, for caliber, weight length etc,
and when he got close to the dimensions, he would repeat the vise/ring trick etc to get where he needed to be.

He had spec's noted in his log book, which he would never show me, or Skip Talbot (50 cal fame/record holder),
even thou they were partners etc, I just found his original reamer print for the Ugalde (TCU) cases,
he used 1 reamer to make all chambers/calibers from 22 thru 30,
quite an ingenious Basco, he started me in GSing, may Wes and Skip always RIP.  :(

Tia,
Don
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