Barrel Tuners (not rimfire)

[Tony Z]

As someone who tried tuners on barrels 20 years ago only to ultimately utilize the thread for a stretcher tube and never look back, I'm going to revisit a barrel tuner again. Specifically on a heavy gun.
While tubes have never failed me in the past, the possibility of positive compensation is not easily envisaged because a tube is a structural beam that reduces both droop and amplitude.
What i intend doing is replicating the method i did with a rimfire where i got 1045 Tenex and 1065 Tenex to converge at 100 yards to then shoot both 1054 Tenex and Black into flat wind reads. I recently saw a detailed report on a barrel blocked centerfire rifle doing exactly the same thing with a large powder charge variation in the upper and lower.

Now this is the question. While the 9th harmonic is used with success in rimfires, what harmonic is best suited to a centerfire? I have read of 19 and 21 where old Trev said he uses 21, but i have now found some using 7. Some have tried 8 with success which runs outside the theory of quarter of the harmonic where the muzzle would lie at maximum amplitude and thus at exactly the point that would determine the worst accuracy.
If 7 worked in some applications it would appear that the frequency is either less than some assume or it is a third of the 21 Trev and others use and by pure luck someone tripped over a tuned barrel. I can see why 7 can work and can even see the advantage of it and even as low as 5 giving a much wider node that is far less sensitive to both temperature and velocity changes.
Has anyone tried a tuner on their gun like i know Rod and Trev have and what harmonic if any showed promise?

[LoneRider]

this seems all well above my pay grade

[trevort]

this seems all well above my pay grade

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[The Raven]

this seems all well above my pay grade

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Ditto! All I could figure out from that is that I need to buy some 9th Harmonics. Does that come in spray can?

[Rabbitz]

Hi Tony,

I can't answer your question, however I do have a question for you.

If people are in fact tuning the barrel to create the 9th harmonic (or any harmonic) anti-node at the muzzle, that suggests that there is, in fact, a standing wave being created.

Given the nature of the detonation, the inertia of the barrel, the changing mass and moment of the system as bullet and gas move along the bore and the very short timeframes for this wave to be created and destroyed, has anyone actually measured the standing wave?

[justjeff]

Tony,

I will be building my test rig starting tomorrow, so we can have a good play with the numbers. I will be keen to see if a 100mm square by 200mm long barrel block can influence a 50mm barrel, shooting a 187 gr bullet at over 3k fps.

Jeff

[Tony Z]

Rabbitz the PRX formula seems to work for rimfires and the Hoehen /Harrel tuners working with barrels around 24 to 26 inches long. Basically a standing wave formula where the muzzle is placed at what some refer to as the parallel node. Very reliable on rimfires using the 9th harmonic calculation.
When it comes to centerfire it becomes vague. There seems to be no cut and dry recipe.
I spoke to old Trev and this is what he did but without an actual tuner.
From muzzle where the bullet actually departs the bore to breech face is say 30 inches for ease of working here. Using 21 harmonics. Subtract 1 harmonic equals 28.572". So his physical barrel length from breech face to the point where the bullet exits the bore is now going to be 28.572" remembering he is not adding an actual physical tuner.
OK so now we start with the 28.572" as if we were about to calculate a total barrel and tuner length so it is divided by 20 harmonics giving 1.4286". That is now multiplied by 21 giving roughly the 30 inches we started with. His counterbore diameter is 0.792" (end bore like that of an actual tuner like a Harrel etc) where that is multiplied by 0.3 (a constant for end correction) giving 0.238". That is subtracted from the 21 harmonics or 30" giving us a final physical tuner and barrel length of 29.722". The barrel is trimmed to that exact measurement from breech face. The muzzle is now counterbored to the 20th harmonic or 28.572" or more to the point the 20mm endmill he used is sunk in 1.15".
So in essence what Trev did was do a calculation for a tuner length without using an actual tuner where he used the barrel material to create what a tuner does. His muzzle is sitting 1.15" in from what appears to be an unmodified barrel.
I am doing exactly nothing like this.
Confused yet?

The point is Trev says this rifle shot the original worked up load into very small clusters. So for him the 21st harmonic seemed to work. But as i said some have used 7 right through to 27. Big fucken change in counter bore in Trevs case had he used 7. He would have had to use a U drill for a counterbore of around 4.5" Fuck that. I'm using a physical tuner and about 3 inches of thread and tuner extensions if i need the length. That way i can run through a number of harmonics in a session. But it would be nice to get some feedback.

[jacko-2]

i use the fith elememt system, if it dont shoot sell it to some one u hate,,lol been at this subject for awhile now with matt,, doesnt seem to matter barrel length , but the thinner better,,to a point,,the most interesting thing about this is that u dont have to move it much to see a change, two ways to use them,, use a crony and get the ES you wont , then turn the tuner to tighten the group,az u know the best numbers dont always match the groups,,
second way iz to tune az normal and refine it with the tuner,,this iz more for barrels that go from horizontal to vertical with out clustering,i hav had and got some barrels that do this , az does matty, he put a tuner on them and they turned into some of the most accurate and consistant barrels he haz had,,only draw back iz he hates making and fitting them ,,he carnt get wot iz needed to be paid for it,,and if someone walks past and gives it a tweek,,but they work,,

[Brad Y]

Have played with a few things over a few years, fixed weights, adjustable tuners then adjustable tuners that have some dampening material on them.

In the end I have found 2 ways to play.

PC you can go for but in the end I feel that the point of compensation is often shorter than 1k and while it helps, it might not be 100% foolproof. There’s always a chance a barrel will have a negative or neutral profile then your up for rechambering or extra work. Not all barrels will show PC. If you can get PC and a low spread I reckon this would be perfect. For me the chances of that happening would be rare but for others they will probably get it every time. Bloody Murphy

I’m now using the adjustable tuner and doing the usual primer, powder and seating depth then going back to tweak the tuner at the end. Have given up trying to understand different harmonics and such. Load it and shoot it at 1k, get it shooting flat and as small as possible then spend time on the trigger. Feeding a barrel what it wants not what I calculate or think it wants is a lot easier and doesn’t make my head hurt with maths and physics.

[Tony Z]

Brad i sort of agree with what you said at the end. There is reference to so many theories it makes one wonder. But i recently read a report on a blocked rifle that tuned to a velocity spread rather than a velocity specific. The idea was to have a rifle that shot at all weather conditions. The result, this particular result, showed a low velocity shot and high velocity shot converge. It also showed how it can diverge.
Im not interested in a blocked barrel but what i am interested in was the result.
The addition of weight to the muzzle induces a more vertical shot pattern. Standing wave or angular don't matter. One plane can be dealt with. Multiple planes need mid tuners or dampers like the Sims.

[Brad Y]

I used to have a barrel blocked rifle and it shot well. I think if you had it set up to do it, you could have the barrelled action able to slide back and forth and tune it that way. I could adjust a couple of hundred thou forward or back since there was no recoil lug and the trigger recess was cut out generously.

I’m toying at the moment with a dedicated LG 1k and 500fly build which will mean the Barnard action will need a lighter stock and will have to order a different reamer and dies for a different cal. A tuner brake will be my choice.

[justjeff]

Brad, that is exactly what I am building at the moment, a rig to be able to move the barrel in the block, from breach to muzzle, and still be able to shoot it. Only challenge is it's a 50mm straight barrel.
Jeff

[Brad Y]

FARK...

I would still like to do a stretcher tube FS gun but time and funds and blah blah

[RDavies]

Brad, that is exactly what I am building at the moment, a rig to be able to move the barrel in the block, from breach to muzzle, and still be able to shoot it. Only challenge is it's a 50mm straight barrel.
Jeff

Do you mean the barrel will recoil back through the tube, or do you mean that you will be able to loosen the clamp and move the barrel back and forth in the block as a form of tuning?

[RDavies]

FARK...

I would still like to do a stretcher tube FS gun but time and funds and blah blah

Yes, while I have tuners on pretty much everything, I wouldn't mind playing with a stretcher tube. Maybe on an upcoming f/tr build, either 223 or 308. Tony, what are the pros and cons of a stretcher tube over a tuner?