Tuners and Barrel Harmonics
- Thread starter JAS-SH
- Start date
Well got a call i had to work tomorrow so ran out today to test 3 lots of 6.5 Creedmoor ammo. Rifle was clean and had just switched back barrel so needed to rezero and foul so used a lot that shot good but I only had a little left. Got zeroed and shot 5 shots into a bullet hole that was there from zeroing. Didn't touch the tuner at all. That was first pic.
Then I pulled out another lot and it took two targets. Left is first two shots and then right is the next two shots.
Then last pic is a lot that never shot great but I wanted to test it. Unfortunately I grabbed a partial box so only got 7 targets shot but it started to come in on 6 and 7. Will test again next time out.
All in all I am very happy with this KSS tuner. That barrel has a little over 2100 rounds through it and still shooting pretty good.
Then I pulled out another lot and it took two targets. Left is first two shots and then right is the next two shots.
Then last pic is a lot that never shot great but I wanted to test it. Unfortunately I grabbed a partial box so only got 7 targets shot but it started to come in on 6 and 7. Will test again next time out.
All in all I am very happy with this KSS tuner. That barrel has a little over 2100 rounds through it and still shooting pretty good.
Make fun all you want about tuners......yes they are not very sexy at the end of a barrel but IMO they work .....proven through results. I have seen great results since I bought one....I would recommend trying one you may be surprised.
Harmonics? Just put an interrupted thread on the barrel exterior. Having loads of time now that I'm retired, I read a lot. Saw a website teeming with technical language but was able to boil it down and make it simple. Just threading the outside of your barrel will increase the surface area >100% An interrupted thread deadens harmonics. My approach? D, all of the above. I have an interrupted thread pattern 2,5,1,1,2,4,3 where one of the 1's is no threading. I have 8, 10 and 12tpi and randomly alternate right and left hand thread. Stepped down 1/16" and did it again, etc. If there's anything to it at all, I at least have the cooling. Pic below of the 300NM experimental barrel I made for my own use in the garage. Both this and my 6XC barrels shoot better than I do.
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Nobody? Well either you all are out threading barrels or you died laughing when you saw this ugly thing
Set it up for a tuner.
Then do tests and see if seating depth or the tuner change poi and group size.
I shoot three different bullets in my 6xc, I've managed to keep the group sizes <=1/2 MOA ,Vertical varies per bullet about 1/2" between the three. So no, not perfect. 300NM I only shoot 230 Bergers. Why mess with a 1/2 and 1/3 MOA(respectively) rifle?
Tuner: well if you add a weight to the end of your barrel, of course it will change the POI. Change weights location, change POI.
^^^^^^^^^^^^^^^^
not getting a tuner
vvvvvvvvvvvvvvvvv
Seating depth did change the size of the groups
Perhaps someone whose won the lottery can run all the tests one day. As is, is good enough for me.
Should I just agree/disagree? Both barrels shoot well; is it better is the question. I don't care.
It didn’t “Deaden the harmonics” or at least not in a way that makes it worthwhile.
You cut threads into a barrel to make it shoot the same as a barrel without threads.
The comparison you made between AK barrel flex and and the Barrett is apples to oranges. The Barrett is bigger and fluted, but most importantly it doesn’t have a piston out near the end of the barrel cycling the action. The downward moment of the AK barrel is almost entirely caused by that. 7.62x39 in a pencil barreled bolt gun would look completely different.
Tuners can be set to reduce wind sensitivity, or exaggerate it. Trade off is vertical in the group vs flat waterline with extra driftA windage/tuner one two punch might be interesting
I was talking about a combined assault on the windage dial and tuner to to amuse me at the cost of others.
Sometimes you want the slower rounds to exit when the whip points the muzzle higher than the faster loads. This can be tuned at a specific distance. Relevant for one way range paper punching. There is always some ES
There was a time when every other person at the range I belonged to had these. Yucky.
Yucky is right - but I had a co-worker that tried one on a Remington 700 sporter in 7-08, and after a little trial and error in its' placement - we found a spot were the groups with factory ammo went from 1"- 1 1/2" down to a single hole ( 3 shots ) of 3/8" - 1/2" consistently. We felt like we had discovered the promised land.
Funny, though, it was his deer rifle, and most shots around here are less than 100 yards ( most are probably 50 - 75 yards ). But he did enjoy bragging about the groups to anyone that would listen.
I'd rather walk around and claim I had buck fever so I didn't take the shot than let a bunch of hunting buddies see me with a rifle that has a butt plug on the barrel by the stock 
Not meaning to join a food fight.
This academic paper might be helpful in this discussion:
Graph below was copied from the original publication:
Quoting from the paper (items in brackets are my clarifying additions):
“In the image (above), the top (blue) trace is the barrel vibrations from the bare barrel, discussed above, and the bottom (blue) trace is the barrel which has now been "tuned" with a 200 gram weight attached to the front of the barrel. The traces have been superimposed so that the bullet exits appear at same time (NH: The dip in the red trace, when the bullet flies through a stationary beam of light). As can be seen, the general shape or pattern of vibrations for the two traces is very similar. However, while the vibrations on the two traces start out in a very similar way, the pattern of vibrations with the weighted barrel appears slightly stretched in time compared to that of the unweighted barrel.” Credit to Mr. Geoffrey Kolby, you did real good work sir!
[You can think of a ladder test as moving the red trace forward and back (barrel time varies because speed varies) to line up with an upward swing in the blue, which is hopefully “wide” to achieve positive compensation. Minimum SD might well not line up. Tuning seating depth changes the timing of of the pressure peak in the chamber via an ignition delay (but speed could be kept the same as before), so that moves the blue line forwards and back.]
Conclusion: Turning a barrel tuner to move the tuner weight forward, even by a tiny amount, slows down the barrel vibrations (dominant slow mode and the higher frequency modes) a tiny bit allowing you to get bullet exit at a point in the blue curve where positive conpensation benefits can be exploited, without the need to tune the load via powder weight changes. (Which is a benefit if you shoot factory ammo at fixed distances, or want to do load development on a hurry.)
This published article is a little academic, but it successfully demonstrates a high speed optical method for measuring barrel vibration at high scan rates using a digital oscilloscope. Worth reading.
Using the data the researcher collected, he predicted what barrel whip speed (the required rate of upward movement) that would yield the smallest group size for a particular distance, and it actually worked as predicted. [You need to find a segment on the blue graph where the rate of upwards barrel movement equals the specific calculated slope needed for that shooting distance, and the time range is as wide as possible, for positive compensation to kick in. A very different distance will need a very different slope and a completely different tuner setting. The science works, but very few of us have fully instrumented rifles (yet), so not yet practically usable. Some bright entrepreneur with an electronics background might just take this idea and run with it....]
It appears to me that this is a case of: Theory proposed. Prediction made. Experiment conducted to the test theory. Experimental result agreed with the theoretical prediction, so conclusion has to be that the theory has value, even if it is an approximation to reality.
I have installed a KSS barrel tuner made by Aaron Hipp a week ago, and as i adjusted it the very first time, my groups first got progressively bigger but after a few more hash marks, the groups got smaller and eventually much smaller. If you keep turning, then yes group size will open up again and after a while close in again. The results published above predicts that every one of the minima you discover will yield a different group size. Your best group size might be multiple turns away. My biggest group was around 2 MOA. Smallest was around 0.25 MOA prior to optimizing seating depth.
Then optimized seating depth (for very long jump, so it will feed from the mag) with the tuner at the prior best/optimal value. Shot a best group of 0.15” c-2-c on Saturday. Maybe just lucky and yes more testing is needed. But happy with that for now.
Zero optimization of powder load so far, although loaded to 0.02 gn accuracy on an FX120i scale, which the factory will likely not achieve. I was just trying to simulate factory ammo, which i can seat deeper if I choose to. Seems to work.
A tuner is just another handy tool in the proverbial toolbox that is useful if you want to shoot factory ammo.
Edit: And for handloaders in a hurry, like me.
This academic paper might be helpful in this discussion:
Graph below was copied from the original publication:
Quoting from the paper (items in brackets are my clarifying additions):
“In the image (above), the top (blue) trace is the barrel vibrations from the bare barrel, discussed above, and the bottom (blue) trace is the barrel which has now been "tuned" with a 200 gram weight attached to the front of the barrel. The traces have been superimposed so that the bullet exits appear at same time (NH: The dip in the red trace, when the bullet flies through a stationary beam of light). As can be seen, the general shape or pattern of vibrations for the two traces is very similar. However, while the vibrations on the two traces start out in a very similar way, the pattern of vibrations with the weighted barrel appears slightly stretched in time compared to that of the unweighted barrel.” Credit to Mr. Geoffrey Kolby, you did real good work sir!
[You can think of a ladder test as moving the red trace forward and back (barrel time varies because speed varies) to line up with an upward swing in the blue, which is hopefully “wide” to achieve positive compensation. Minimum SD might well not line up. Tuning seating depth changes the timing of of the pressure peak in the chamber via an ignition delay (but speed could be kept the same as before), so that moves the blue line forwards and back.]
Conclusion: Turning a barrel tuner to move the tuner weight forward, even by a tiny amount, slows down the barrel vibrations (dominant slow mode and the higher frequency modes) a tiny bit allowing you to get bullet exit at a point in the blue curve where positive conpensation benefits can be exploited, without the need to tune the load via powder weight changes. (Which is a benefit if you shoot factory ammo at fixed distances, or want to do load development on a hurry.)
This published article is a little academic, but it successfully demonstrates a high speed optical method for measuring barrel vibration at high scan rates using a digital oscilloscope. Worth reading.
Using the data the researcher collected, he predicted what barrel whip speed (the required rate of upward movement) that would yield the smallest group size for a particular distance, and it actually worked as predicted. [You need to find a segment on the blue graph where the rate of upwards barrel movement equals the specific calculated slope needed for that shooting distance, and the time range is as wide as possible, for positive compensation to kick in. A very different distance will need a very different slope and a completely different tuner setting. The science works, but very few of us have fully instrumented rifles (yet), so not yet practically usable. Some bright entrepreneur with an electronics background might just take this idea and run with it....]
It appears to me that this is a case of: Theory proposed. Prediction made. Experiment conducted to the test theory. Experimental result agreed with the theoretical prediction, so conclusion has to be that the theory has value, even if it is an approximation to reality.
I have installed a KSS barrel tuner made by Aaron Hipp a week ago, and as i adjusted it the very first time, my groups first got progressively bigger but after a few more hash marks, the groups got smaller and eventually much smaller. If you keep turning, then yes group size will open up again and after a while close in again. The results published above predicts that every one of the minima you discover will yield a different group size. Your best group size might be multiple turns away. My biggest group was around 2 MOA. Smallest was around 0.25 MOA prior to optimizing seating depth.
Then optimized seating depth (for very long jump, so it will feed from the mag) with the tuner at the prior best/optimal value. Shot a best group of 0.15” c-2-c on Saturday. Maybe just lucky and yes more testing is needed. But happy with that for now.
Zero optimization of powder load so far, although loaded to 0.02 gn accuracy on an FX120i scale, which the factory will likely not achieve. I was just trying to simulate factory ammo, which i can seat deeper if I choose to. Seems to work.
A tuner is just another handy tool in the proverbial toolbox that is useful if you want to shoot factory ammo.
Edit: And for handloaders in a hurry, like me.
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Not necessarily just for factory ammo. I never shoot factory but im considering a tuner. It may give me the choice to tune my barrel to the speed I want to run nit the other way around. My dasher shoots in the .1s but it is very fussy. I only seem to have a high node and can't get any accuracy I'm happy with running slower. I'd like to drop some velocity but I can't without loosing accuracy
Agreed.
IMHO, if you are an experienced BR guy that has been reloading at the bench for years, you probably do not strictly need a tuner, because you can most likely achieve the same/similar results via powder charge and seating depth optimization. But it is another degree of freedom to exploit, and is very quick and convenient, but not the proverbial ‘silver bullet’.
And from my limited 2 weeks of experience, yes it can help the reloader-in-a-hurry (like me!) who has limited time and does not want to do endless load development (burning up barrel life), or reload at the bench. I have done a few seating experiments at the bench, and it worked, but it is rather inconvenient to carry powder and a scale to the range, too much kit needed and wind negatively affects the accuracy of the scale. But more importantly, people look at you real funny...
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