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Barrel Harmonics, the DEAD barrel?

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nomojo65

nomojo65

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Dec 3, 2015
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Great Lakes, United States
Thought it would be interesting to start a new thread on this subject, your thoughts, experiences knowledge etc. in the airgun world what constitutes a harmonically neutral barrel? (If there is such a thing). 
People talk about shrouds, sleeve’s, (type’s of materials) tensioned, compressioned, weights, the list goes on and on.

My experience’s with the guns I’ve owned the RAW’s both titanium and CF sleeved (with Moderators and not) and the AAA evol seemed the most stable and predictable of all other’s I’ve owned and shot. 
Please weigh in I’m infatuated with this subject!
 
All gun barrels, whether air or powder, will vibrate during the shot cycle. The goal is to minimize that vibration. The best way is to increase it's mass or provide a dampening device. It's great to see FX coming out with vibration dameners. Powderburners have been using them forever and it's about time we get them. I used to use those heavy rubber weights on my TM1000 for BR shooting. They seem to help, but it's hard to quantify.
 
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Joe, there are 2 competing theories for the use of barrel tuners in Rimfire. The theories will also apply to air. I got a kick out of the FX review for their new tuner that claims it performs both.


1. The stopped muzzle theory. (Bill Calfee)…you will have to buy his book The Art of Rimfire Accuracy to get all the info in one place. You can get tidbits of it by reading forum posts at many different sites. In essence, Bill suggests that only the addition of a specific amount of weight in FRONT of the muzzle can create a truly stopped muzzle. All Rimfire tuners overhang the muzzle. There are also formulas to compute this weight and distance….the Purdy Prescription. Searching these terms will give you a lot of info.

2. Positive compensation. (Geoffrey Kolbe) http://www.geoffrey-kolbe.com/articles/rimfire_accuracy/tuning_a_barrel.htm

Positive compensation surely seems a valid theory as well since there is a ton of evidence for tiny vertical displacements in rifles that have relatively large velocity spreads that do not suggest that such vertical is a ballistic possibility without some other mechanism.

Its a deep hole.

Mike 




 
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From what little I know of the rimfire shooters is they can also tune for different lots of ammo with these tuners, which actually is what intrigues me the most I guess.

I’ve experimented a little with a simplistic delrin weight on the end of my barrel but with no conclusive results, but these didn’t extend past the barrel.

I also shoot against three of your rifles two with shrouds FT versions the other the BR. Their accuracy is equal! Paul B. has made his own version of tuner that closely resembles the RF tuners.

I know you’ve done your own testing, not sure your conclusions, but I know most of your Guns I see have no tuner! I believe you have done the barrel tuning before these guns leave your shop!

Thanks for your input and I will be buying Bills book! 
I hate that unexplainable flyer that is almost always vertically dispersed, ruined many good cards!
 
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Looking at the upper echelon of powder burners, we can conclude the preference is for thick, heavy barrels. In that world we aren’t going to find any soda straws centered in a tube by a few O-rings. Similarly, we won’t be finding barrels secured with an M4 grub screw or two. Instead they are firmly anchored to the receiver…usually threaded which makes the already heavy barrel behave as an even larger mass. Granted, they are dealing with massively elevated excitation forces that set up vibration. 

For our pea shooters, it’s kinda hard to justify strapping on a 6lb bull barrel. At least not for any product the designers wish to be commercially viable. Stuff like that is in the realm of custom builds. A cost-no-object, don’t care what it weighs, gonna live its life on a bench sort of thing.

For a gun we plan to lug around, some degree of compromise is helpful. Like you said, both tensioning and carbon fiber sleeves are successful approaches. Either one can be done for a similar cost. So absent any meaningful cost difference, if one were superior in performance, the other would have faded into obscurity. That hasn’t happened so it seems to me they each carry a similar potential to improve things.
 
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Rigidity is the name of the game. One thing I love about my Taipan is that the barrel is decently thick and, due to the bullpup design, the barrel only extends a few inches past the rail clamp, making it very rigid. I have been known to cut down longer barrels on low power airguns to get a stiffer barrel. 

Jason mentioned barrel attachment methods and I think most airguns don't have a great way of attaching the barrel, generally a few grub screws. Another thing I love about my Taipan, barrel threads into the receiver. 
 
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I could fall so deep in this it's stupid. Not just the vibration aspects but all facets of accuracy improvements. "For our pea shooters, it’s kinda hard to justify strapping on a 6lb bull barrel. At least not for any product the designers wish to be commercially viable." But, on the other hand, product development is all creeping right past thoughts like this. If interest is there and popular enough commercial offerings will show up.


 
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There ARE guns out there that are doing this.

This is a .900” barrel with a solid action block and 4” of full contact. 

Mike 

885354C3-3790-4586-8922-3EECA2B31AAC.1625322831.png

 
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product development is all creeping right past thoughts like this.
Click to expand...

Well, the ideas and prototypes that didn’t make it to production are unknown to us. I would not presume the likes of Daystate, RAW, FX, etc. have left this avenue unexplored. It is rather more likely they have experimented with a dizzying array of barrel shapes and sizes and retention methods, shrouded and unshrouded, tensioned and untensioned, sleeved and unsleeved.

What I was trying to draw attention to in my earlier reply is that commercial product design is about balancing compromises. Here we are talking about the extent to which various approaches make a rifle more “harmonically indifferent,” so to speak. So for example if the engineering team finds that doubling the weight of the barrel makes a demonstrable improvement in this respect, but the added weight simultaneously narrows its prospective market to a relative handful of professional benchrest shooters, it probably ends up on the cutting room floor.

Food for thought. Why not have a 25mm diameter barrel with a carbon fiber sleeve bonded to it, then tensioned to the receiver?
 
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Is this a airgun forum? Not a center fire unlimited rail gun forum?, I just wanted thoughts and theories and experiences of “airgun harmonic tuners”. This subject intrigues me.

If I had machining skills I would experiment with more sophisticated types of tuners than I have been. For now I’ll have to make do with the rudimentary type.
 
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From their website.

"Volquartsen Carbon Fiber 10/22 Tension Barrels
Threaded Tension Tuned Match Grade Barrels w/Optional Muzzle Brake

The Volquartsen approach to making a lighter weight barrel for the Ruger 10/22 is unique... They use a tensioning system to enhance the accuracy and cooling characteristics. The stainless steel core of these barrels is referred to as "THM" for Taper Honed Match barrel and chamber. The bore and chamber dimensions vary no more than .0001" from breech to muzzle... That's 1/10,000th of an inch. "Taper Honed" refers to the polish of the bore and the improved transition from the chamber to the bore. Dimensions are confirmed by digital measurements. Length: 16.5", Weight: 1lb. 4oz.

The "core" of these barrels is a small diameter match grade barrel. Now, as diameters get smaller, the potential for vibration increases. So, Volquartsen reduces vibration by TENSIONING the core within a light weight carbon fiber sleeve. The result is a lighter barrel with the same stiffness and vibration deadening as a heavy match barrel... Quite a unique system."
 
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