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The Garage / Re: Another Harmonic Killer Test
« Last post by rsterne on Today at 01:57:12 PM »
The tension required to stiffen a barrel, according to Tom at AAA, is about 800 lbs. of tension, minimum.... This isn't a lot, on 1/2" steel threads, that is about 80 in.lb. of torque, just under 7 ft.lb.... You will be shocked to find that 30 ft.lb. of torque works out to 3600 lbs. of tension on 1/2" threads.... It could as high as 4500 lbs. of tension with the right lubricant....  :o …. You better have the barrel well secured to stand those kinds of loads.... and you may run into the corresponding compression load on the shroud either buckling it, or in the case of carbon fibre, shattering it.... I would not want to be near it, should that occur....

https://www.engineersedge.com/calculators/torque_calc.htm

I run about 1000 lbs. of tension as a baseline with my Belleville tensioning system, and the plan is to adjust to minimum group size.... Tom says that once you get to about 800 lbs. of tension that more makes little difference, although it can change the group size from bullet to bullet.... The largest gain in accuracy is when you go from 600-700 lbs. of tension in the barrel to over 800.... I haven't played enough to confirm that, but it does give you some idea of the tension loads required.... and how LITTLE torque it takes to achieve that....

Bob
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The Garage / Re: Another Harmonic Killer Test
« Last post by Alan on Today at 10:39:42 AM »
The guy to ask is Jim Gaska, but he doesn't check in very often.

The tensioning nut on my Cobra is torqued at 30 foot-pounds. The thread is 1/2x20. On the breach end of the interchangeable barrel, is a compression clip. The tension nut pulls the barrel against this clip using the outer (barrel) sleeve. This sleeve (shroud) is also a chamber for some of the muzzle blast to be diverted down, much as a Marauder does. There is a screw-on suppressor with 5 baffles.

I've played with the tension some, as all Jim told me was that the nut needed to be "fairly" tight. I can tell you, that more tension (up to a point) helps accuracy. To be honest, 20 foot-pounds is enough.

As I alluded to previously, tensioning seems to make the assembly less prone to POI changes caused by pellet weight (heavy vs light).
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The Garage / Re: Another Harmonic Killer Test
« Last post by Motorhead on Today at 10:36:09 AM »
Guys
If I can ask a couple of questions,

Tensioning, a bbl only works on certain type of actions, correct?

For the average AG actions that are mag fed, there is only so much you can do,
because of the mag cutout correct?

I know nothing about tensioning a bbl, only what Bob has mentioned etc.

Tia,
Don

This is IMO somewhat a grey area simply because options do exist to semi permanent install / lock a barrel within the receiver without the need for a Circlip as the WAR guns utilize.
It does not take that much pressure it terms of stretch / pull on a barrel to really get it rigid. Add to that an over tube be it a shroud or sleeve that when the ends of said tube are made to be square with the receiver the barrel is further held square & true leaving the receiver.  End result is one very firm and stiff barrel configuration.

Just sayin ...
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The Garage / Re: Another Harmonic Killer Test
« Last post by Nvreloader on Today at 10:14:42 AM »
Guys
If I can ask a couple of questions,

Tensioning, a bbl only works on certain type of actions, correct?

For the average AG actions that are mag fed, there is only so much you can do,
because of the mag cutout correct?

I know nothing about tensioning a bbl, only what Bob has mentioned etc.

Tia,
Don

 
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The Garage / Re: Another Harmonic Killer Test
« Last post by Alan on Today at 09:40:40 AM »
Scott, I too believe tension is the way to go. My .25 caliber WAR Cobra is amazingly accurate. And it doesn't make much difference what you shoot through it, as long as it is round nosed. This is to say, PolyMags just will not group beyond about 50 yards.
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The Garage / Re: Another Harmonic Killer Test
« Last post by Motorhead on Today at 09:04:04 AM »
Interesting as harmonic dampers are ... in an air gun barrel, Would it not be far better & easier to TENSION the barrel ( As in Stretching it taunt ) by what ever mien required ?

Having fooled quite a bit with the one AG I own that utilizes Barrel Tension .... WAR WarP.  Currently running a full length LW barrel at 23" in .22 caliber and that SOB is the most accurate PCP I own and that's saying a lot !! also owning match grade Daystates & RAW rifles with conventional barrel set ups.

While the WarP is stupid accurate, it is a difficult platform to shoot accurately IMO being it's shape fit & feel are AR-15 based. Tho that is another subject entirely.

Just asking ?

Scott
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The Garage / Re: Another Harmonic Killer Test
« Last post by Nvreloader 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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The Garage / Re: Another Harmonic Killer Test
« Last post by Alan 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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The Garage / Re: Another Harmonic Killer Test
« Last post by steveoh 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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The Garage / Re: Another Harmonic Killer Test
« Last post by rsterne 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
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