Barrel tuners. Good or a waste of time?

[mikeeg02]

Please tell us more. How does stock stiffness or flexibility affect it ?

I would think that's effectively the "rigidity" of the fulcrum (where everything starts). And weight distribution would affect how the rifle would potentially jump in the bag. Someone correct me if I'm thinking wrong.

 

[gunsandgunsmithing]

Please tell us more. How does stock stiffness or flexibility affect it ?

I wish I could explain it better. It's one of those things that I think, if you really understand something, you can explain it in terms that anyone can understand. PC is something, among many things, that I can not. I know enough to be dangerous. I have lots of theories on the subject that need to be tested. Simple as that. The more pc you have, the wider the tune window becomes, though. I'm pretty certain that's why poi matters to node width, per se. PC is IMO, the next chapter in rifle accuracy.

 

[gunsandgunsmithing]

I would think that's effectively the "rigidity" of the fulcrum (where everything starts). And weight distribution would affect how the rifle would potentially jump in the bag. Someone correct me if I'm thinking wrong.

I think you've got the idea.
I just think there's a ton of factors. Search BRC for positive compensation. I can't remember Keith's screen name there either at the moment but IIRC, he wrote some good stuff with numbers and formulas. I'm sorry I can't remember shat. Lol!
FWIW, I think we may have trended the wrong way with stiffer stocks and barrels. Where the perfect compromise is, I don't know that either. On that note, a fatter barrel is NOT necessarily stiffer.

 

[Bart B.]

I remember reading that Positive Compensation was distance specific.
Does the tuner change that?

In my opinion, it is.

Here's two more graphs, one tuned to and zeroed at 100, the other at 200. Note how the vertical spread changes at ranges other than the zero one.

 

[BartsBullets]

Bart, you bring up a good point and are so right; tuner settings ARE yardage specific. Me, being only a short-range group shooter, never realized this until I began experimenting with tuners several years ago and came to a better understanding of what we call 'Positive compensation.' I'm glad to know you are venturing out into long-range shooting. I hope you will keep us informed on how it's going. There seems to be a great deal of interest in long range and extreme long range in recent years.

Thanks for joining our discussions. I understand why you and your 'fast track' buddies wouldn't want you to share too much of what you guys have taken so many years to learn. I do understand; really. We are all different and have our own reasons for pursuing this madness called benchrest. What I must keep in mind is that some people are far more competitive than I am and winning means far more to them than it does to me.

Oh sure,, at one time, when I was much younger, winning was very important to me because I felt I had something to prove but I got over that long ago. During the past fifteen years or so, I find myself more and more just enjoying the study of extreme rifle accuracy and the machining and product development that goes along with it.

It's great to get your input ! Keep up the good work and best of luck in 2019 !

Sincerely, and with best regards.

Gene Beggs

Yeah, that’s Bart B! Not Bart Sauter

 

[Bart B.]

Where the perfect compromise is, I don't know that either. On that note, a fatter barrel is NOT necessarily stiffer.

For a giiven chamber, bore and length, a fatter one is stiffer. It resists bending more than skinny ones. Its bending arc at the muzzle will be less.

 

[Bart B.]

We have pc whether we have a tuner or not. I believe that tuners give us more pc than without and make it possible to get what the rifle/whole package has to offer.

What if all the bullets leave on the middle of the muzzle axis down swing?

 

[Bart B.]

Browing says:

How the BOSS works.

The BOSS simply tunes the vibrations of your barrel. This allows the bullet to leave the barrel the split second it is stationary. Your BOSS manual has a list of settings for each caliber and bullet weight. Adjusting your BOSS to these "Sweet Spot" settings allows you to find the instant your barrel is stationary. The result is accuracy never achieved before by an out-of-the-box rifle.

Years ago, they claimed bullets left when the barrel was perfectly straight.

Does that split second point at the top of the muzzle upswing? Imagine what would happen as bullets don't have the same velocity nor barrel time to the muzzle. But the frequency the muzzle axis vibrates at is very constant across all shots when the barrel is held the same for every shot. Bullets leaving near the bottom still point past it's maximum leave on the upswing; opposite than at the top.

Tried explaining that to Browning; impossible was their response.

For decades, Winchester claimed fluting any one of their round barrels made them stiffer. Contrary to basic vibration analysis and moment of inertia formulas.

 

[gunsandgunsmithing]

For a giiven chamber, bore and length, a fatter one is stiffer. It resists bending more than skinny ones. Its bending arc at the muzzle will be less.

Yes, but not all barrels are the same length. Lilja has a nice barrel stiffness calculator built into his barrel weight program. It's very interesting to play with the numbers. For example, according to the program, a 28" HV is stiffer than a 30" 1.250 straight.

 

[gunsandgunsmithing]

What if all the bullets leave on the middle of the muzzle axis down swing?

Not sure I understand what you're saying but if it's what I think, you're on what some call the "scatter node" and it would take a miracle for them all to go into the same hole.

 

[gunsandgunsmithing]

Browing says:



Years ago, they claimed bullets left when the barrel was perfectly straight.

Does that split second point at the top of the muzzle upswing? Imagine what would happen as bullets don't have the same velocity nor barrel time to the muzzle. But the frequency the muzzle axis vibrates at is very constant across all shots when the barrel is held the same for every shot.

I see lots of ifs and buts, err variables. The barrel doesn't stay straight..that's quantifiable. The part that matters most is the muzzle angle, or the last little bit of the barrel..perhaps the amount of bearing surface length? Would explain it being more difficult to tune long range, long bullets, perhaps.

 

[Bart B.]

Yes, but not all barrels are the same length. Lilja has a nice barrel stiffness calculator built into his barrel weight program. It's very interesting to play with the numbers. For example, according to the program, a 28" HV is stiffer than a 30" 1.250 straight.

That's possible.

I've got resonant frequency numbers for three different barrel shapes and lengths that are all the same.

 

[Bart B.]

I see lots of ifs and buts, err variables. The barrel doesn't stay straight..that's quantifiable. The part that matters most is the muzzle angle, or the last little bit of the barrel..perhaps the amount of bearing surface length? Would explain it being more difficult to tune long range, long bullets, perhaps.

I'm convinced any barrel can be tuned for a range; within reason. Some may need 2 or 3 more between the muzzle and receiver.

Then you would need three columns in your tuner's range zero log; one for each tuner.

 

[Alex Wheeler]

Please tell us more. How does stock stiffness or flexibility affect it ?

My "thoughts"

The "goal" of PC in regards to tuning is to have the part of the barrel that controls the initial exit trajectory of the bullet traveling upwards at the time the bullets are leaving. When exactly in relationship to the point that part of the barrel stops at the top and when those bullets are exiting should control the yardage PC occurs. Sooner for LR and later for SR. It could also occur after that part of the barrel stops at its low point. In which case earlier for sr and later for lr. Barrel contours play a role here, so would hanging weight (tuners) at the muzzle.

The "goal" of PC in regards to building a rifle is to encourage vertical muzzle travel by using the rifles natural rotation around it's center of gravity (assuming the c/g is lower than the bore line (line of force)). If you understand the basic physics of forces and c/g you can see how the location of the c/g will play a role in how much the rifle wants to roll. The forend of the stock is a spring with stored energy that will help the barrel rise under recoil. Flexible stocks store more kinetic energy.

 

[Gene Beggs]

Gene..... Bart B DID make a nice graph but I think you're posting to Bart S

Al, you are so right; my mistake. Thought I was posting to Bart Sauter and was sincere in everything I said. I'm sure it's not the first time this has happened.

And by the way, Bart B; nice chart on Positive Compensation. Let's hear more from you.

Later, Gene Beggs

 

[gunsandgunsmithing]

That's possible.

I've got resonant frequency numbers for three different barrel shapes and lengths that are all the same.

Should tune similarly but are the numbers for just the barrel or the whole gun, on the rest? And, temps change the natural frequency a little bit. We're definitely delving into theoreticals now. These things are great for understanding how a tuner does what it does but pretty useless for actually using one. These are the areas I try to stay away from generally because they just confuse most people and make my head hurt. But it's good for someone like you to play with. A lot of this is roughly calculable. It seems to be right up your alley.

Ultimately, tuners time bullet exit with optimal muzzle position and is basically pretty easy to understand all we really need to know. PC is a different animal altogether. Keep it up!

 

[gunsandgunsmithing]

I'm convinced any barrel can be tuned for a range; within reason. Some may need 2 or 3 more between the muzzle and receiver.

Then you would need three columns in your tuner's range zero log; one for each tuner.

I'm not a fan or believer in multiple tuners but hey, give it a whirl. I believe that the muzzle angle is what matters and you're reducing muzzle angle by essentially stiffening the barrel wherever one is placed behind the muzzle. You can't move a node to the end of a cantilevered beam with a device that is only behind the muzzle.

 

[Bart B.]

Ultimately, tuners time bullet exit with optimal muzzle position and is basically pretty easy to understand all we really need to know. PC is a different animal altogether.

I disagree.

Tuners change the muzzle axis vibration so slower bullets leave at higher angles, faster ones to leave at lower angles, and when perfect, positive compensation takes place to move all bullet impact closer together vertically.

Negative compensation is the reverse.

 

[gunsandgunsmithing]

I disagree.

Tuners change the muzzle axis vibration so slower bullets leave at higher angles, faster ones to leave at lower angles, and when perfect, positive compensation takes place to move all bullet impact closer together vertically.

Negative compensation is the reverse.

I'm not sure where we disagree then. I agree with that statement.

 

[Bart B.]

Should tune similarly but are the numbers for just the barrel or the whole gun, on the rest?

Barrel only.

Use this link to see how stuff other than the barrel changes the muzzle vibration stuff such as the stock center pf mass and total rifle weight.

http://www.geoffrey-kolbe.com/articles/rimfire_accuracy/barrel_vibrations.htm

Mass of whatever holds the barrel will change it as it resists the barrel movement during recoil.