barrel harmonic end goal?

[Stubbers]

can the dwell time be adjusted for the pellet to leave the barrel at one of the nodes or anti-nodes?

Yep, primarily via regulator pressure, and porting for the same pellet weight.

For example a .177 ported to 65% of bore making 12 fpe at 1200 psi will have an entirely different internal ballistic profile than one ported to 85% of bore making 12 fpe at 1200 psi. Likewise one of equal porting making 12 fpe at 1200 psi will have a much different profile than one at 12 fpe and 1800 psi.

Plenum volume will likewise have some effect but is less viable of an approach as simply increasing or decreasing pressure.

-Matt

 

[daddypaddy]

It should be noted that the most accurate 50y rifles in the world (Unlimited Rimfire)....which also happen to be our closest relative due to their projectile material (lead) and weight....do not support any of the theories so far listed and explained in the above posts.

The 100% dominant explanation that is actually supported by real world results on 100% of top Rimfire BR rifles is the stopped muzzle...produced only by adding the proper amount of weight in the proper position in front of the muzzle. Bill Calfee invented the Rimfire muzzle device like 25 years ago and it forever changed Rimfire BR. Do a search on stopped muzzle Rimfire and you'll find plenty to read.

Mike

thanks mike!

 

[thomasair]

I happen to know a couple of the most successful Rimfire BR shooters in the world that never touch their tuners once set....even with multiple ammo lots of different velocity.

For each one of these guys, there is probably a thousand (or more) far less successful guys that can't leave their tuner alone for 5 minutes.

 

[Stubbers]

Rifle Barrel Tuner Vibration Analysis

Barrel Harmonics Are A Lot More Important Than You May Think or Know--Here's Proof

First, I have searched for information for about a year and half on this subject. Some of you may know of something really good I've missed, but the best source I have encountered for information on this topic is Al Harral. Who is Al Harral? Al Harral is a retired guy--but one smart...

www.longrangehunting.com

(source, above link)

I personally enjoyed these reads on the subject matter.

 

[thomasair]

The link provided earlier about the stopped muzzle isn't very informative. This has enough to understand the concept.

The Art of Rimfire Accuracy

Bill Calfee has been working with guns since the 1970’s and decided to focus on the 22 rimfire beginning in the 1980’s. Since the 1980’s Bill has had many ideas on how to improve the accuracy of the 22 rimfire, some ideas have increased the accuracy potential tremendously and some ideas proved...

books.google.com

 

[thomasair]

If you click on the link it should go to the muzzle device section.

 

[lbc_PSI]

If the muzzle weight is just keeping the muzzle in the same location, isn’t something like the way RTI barrels are centered/trapped in the shroud kind of the same thing?

 

[tor47]

I am not an expert, but on aiguns we change the harmonics by simply changing the velocity of a given pellet by lowering or increasing the hammer strike. If we only change the hammer strike force, we change when the pellet leaves the muzzle after trigger is pulled. But we also change when the valve close, and the amplitude, and frequency of the "shockwave".
We also do the same if we lower or increase regpressure. Probably more is happening in an airgun than in a powder burner, because we have more mechanical parts moving inside the gun during a shot, as many things are happening at the same time.

When tuning for pellets, I usually just try different speeds between 800, and 900, by using a combination of regpressure, and hammer strike, and choose watever velocity gives best group on target. I find it more difficult to pick a certain speed, like stick to 880fps, and adjust the gun for that speed, than simply choose the speed the gun likes in a given range.

 

[Freddy J]

I have have of Bill's first tuners, and it is not anything like the one invented by Boss that was on my hunting rifles back in the late 60's

 

[JimD]

I am a retired mechanical engineer and discussions like this interest me. But my sense is that barrel tuning, by whatever method, is only important for people who need the absolute best accuracy. Like competition benchrest shooters. I also question the significance further for airguns where the pressure pulse from the gas release is a lot less violent than the combustion process in a PB. Stated another way our gas pressure does not exceed 5000 psi whereas even a rimfire can be as much as 24,000 psi. Center fires double that or more. So the hammer on the barrel (the pressure pulse) starting it ringing is much, much, less in an air rifle. This is not correct but my mental analogy for what is going on is a hammer hitting the end of the barrel. That tends to make it want to vibrate. How much is a function of how flexible it is and how long it is. Tuners mess with this. It may be possible to get a barrel to vibrate in such a way that the vibrations cancel each other out. Could work a little like noise canceling headphones. That seems like a lofty goal for a simple mechanical device but maybe. The cynic in me wonders why all competition benchrest shooters do not use the same device or why the ones using the "correct device" do not win all the matches. It could be just the point I made first. This is not an overwhelming influence on accuracy, many other things are important too. I'd have to get a lot more consistent in my trigger pulls before something like this could meaningfully improve my scores. Still, it's an interesting topic.

 

[thomasair]

Which do you think has more going on before the projectile even starts moving? Air, Rimfire, or Centerfire?

 

[JimD]

Airguns are more mechanically complex in the firing mechanism. There is thus more going on before the gun fires.

I had an experience today that is, I believe, a form of how vibration affects accuracy. I am unlikely to every own or use a FX barrel tuner as you might gather from my previous comments. Such devices attempt to change the point the barrel is in it's vibration pattern when the projectile exits (I believe). I do not know if it works, I've seen others say they saw small effects so I would guess it does. But I just think I have bigger issues to address. But that does not mean that I believe vibration plays no role in my airguns accuracy.

I shot 4 30 yard challenge targets yesterday. 3 were over 195, one was a 189. The low one was with an airgun that has previously produced a 200. It is fully as accurate as the 2 other guns I shot yesterday. But why did it give me a lower score? I cleaned the barrel this morning and checked all the screws in the scope mounting for tightness. Then I shot another target and it was a 186! I kind of did not believe that cleaning the barrel was going to help and it did not. But then I noticed the screws attaching the wood stock to the action were not snug. They were not falling out loose but they were not as tight as I think they were when I installed that stock. I made it earlier this year and the wood was under 10% but it's been sitting in my air conditioned house and my guess is the wood has dried a little more. In any event I snugged up the screws and shot another target. It was a 197 - as good as I've done with this rifle this year. There is some randomness in my shooting, of course, but still I'd shot several targets in the 180s recently with that rifle and now it goes back up over 195. Only thing changed was the stock screws were tightened. I don't think stocks are nearly as important on an air rifle because they typically do not touch the barrel. But when you tighten a metal action into a wood stock it does dampen vibration in the metal action. I think that is what happened today. The stock being loose was permitting more vibration in the action and that affected accuracy. Snugging up the screws stiffened the system and wood is a decent vibration dampener.

I believe vibration affects accuracy but I'm skeptical that add on devices can have the kind of effect I observed today from tightening up my stock screws. I've never seen a review that produced this sort of an effect.

 

[thomasair]

If you are saying that adding a tuner won't fix something else wrong with a rifle we are in complete agreement. The fact is that almost every rifle that can be bought has a lot wrong with it to begin with...so adding a tuner will have no lasting and repeatable effect. That doesn't mean they are useless...they are just usele ss on those rifles.Its like putting a tuner on a 10/22 and expecting it to shoot like a 2500x or a Turbo.

 

[Freddy J]

I find the Ammo and Barrel, are most important. A tuner will not help a bad barrel or bad ammo, shot lights out. Good barrel, it get easier, great barrel and great ammo are what is winning and that's also with an aray of tuners. I found that too heavy a tuner is not as accurate as one the is the correct length. I all boils down on how much do you want to spend.

 

[daddypaddy]

Which do you think has more going on before the projectile even starts moving? Air, Rimfire, or Centerfire?

i would say air. i’m imagining it’s because the gas is expanding at a much slower rate than PB. would the slower expansion rate of the compressed air vs the combustion of PB gasses exaggerate the amount vibrations introduced in the entirety of the airgun system?

 

[JimD]

I cannot prove this but I would be surprised if a barrel tuner could give me 8 points on a 30 yard challenge target. At my level of shooting I would be really surprised to see any change. I'm not saying it won't do anything, just that the effect will not be large and may be overshadowed by the variability in my shooting. My guess is a really good shooter might gain a point or two at most. Might only gain a point on some targets. Longer distances could definitely increase the potential benefit.

 

[Freddy J]

Tuners are not for all airguns, I only use them for Bench rest matches where .001" could make the difference between 1st place or 1st looser. I do't worry too much about anything Minute of Squirrel.

 

[Jaxjax]

It should be noted that the most accurate 50y rifles in the world (Unlimited Rimfire)....which also happen to be our closest relative due to their projectile material (lead) and weight....do not support any of the theories so far listed and explained in the above posts.

The 100% dominant explanation that is actually supported by real world results on 100% of top Rimfire BR rifles is the stopped muzzle...produced only by adding the proper amount of weight in the proper position in front of the muzzle. Bill Calfee invented the Rimfire muzzle device like 25 years ago and it forever changed Rimfire BR. Do a search on stopped muzzle Rimfire and you'll find plenty to read.

Mike

I was to pick up a Harrels for my .71 & .75 OD barrels on a BM500x RAW. Does anyone use the Harrels tuner anymore in rimfire.? I fugure it can't hurt tp try the experiment & not too many $

 

[thomasair]

Unlimited Rimfire shooters still use the Harrels muzzle device....but they use .900" barrels and have very little muzzle blast.

 

[tor47]

We

Longer thinner barrels will have more harmonics/be more sensitive to a tune than a shorter thicker barrel. A true tensioned barrel will stretch the barrel which will reduce said harmonics more than a bare barrel which makes them even less sensitive to tunes. Also generally the more power you put out the more the harmonics there will be. Accuracy is the main goal getting that projectile to exit the barrel at the exact same harmonic node every time.

I have often thought about that. If we compare it to stretching a guitar string, the frequency will increase as you stretch it, and at the same time it will swing less.
Trying to hit a faster swinging node is probably a litle more difficult? But at the same time will be a litle more forgiving if you are completely off the node? A thinner/longer barrel would then be even less acurate when being off the node, as it will swing more, but will then be more accurate on the node, as some velocity change will have less impact?