Math, science, and barrel fluting

[dcali]

No wonder I never made it through engineering school! Damn math! how can they call it math when it is more letters and symbols than numbers Also, damoncali, were you ever a teacher? I actually understood most of what you were saying.

I was at best a C+ math student, and only made it through out of sheer stuborness. I believe I failed calculus twice and thermodynamics once. But no, I've never been a teacher. I do like to write about complicated engineering topics for an audience without an engineering background. I figure if I can't explain it without resorting to math, then I don't really understand it. So it's a way of educating myself.

Also, back when I was an actual engineer and not just pretending on the internet, I would run across engineers who got so technical and were such poor presenters that even other engineers couldn't figure out what they were talking about. This annoyed me greatly, especially when you consider that working in aerospace means working with a broad array of people and backgrounds - bureaucrats, engineers, managers, and technicians (who were greatly underappreciated!). Not every engineer remembers what they learned in college - usually they become managers. Some of the techs had so much experience that you basically had to fight over getting them to work on your stuff since every engineer with a brain wanted to use them. I quickly realized that to be good at things that are technical, you have to be able to de-technobabble it and talk about it in a way that's accessible. "Trust me, I'm an engineer" are words you *never* want to say or hear. I think it's condescending and lazy thinking. If I have to resort to punting like that, it means I haven't done my job well. Some engineering detail is just inherently arcane and mathematical. That's just life. But the vast majority of concepts are understandable in plain English, or at the least with some pretty basic high school math.

So I try. I don't always succeed, but I find it's worth the effort. Every time I spit out a giant post like that, I find that something new clicks in my head.

 

[Nature Boy]

Some of the best engineers I’ve worked with over the course of my career didn’t have degrees, and the degreed engineers that worked with them became better engineers because of their mentorship

 

[TC260]

Every time I spit out a giant post like that, I find that something new clicks in my head.

The best way to learn is to teach. It forces us to organize our thoughts.

...and as a 35 yr old student I also failed calc II twice before getting my act together

 

[jelenko]

why seating depth matters so much

I've assumed that seating depth is a way to time the bullet's exit from the muzzle - no? I.e., trying to match up the bullet's exit with a 'quiescent' time for the muzzle.

If I've got it right, it's about 30 nanoseconds for the pulse to travel from the breech to the muzzle - with a round trip being 60 nanoseconds With a pulse as complex as I imagine the fast burn rate/slow explosion would be, it's probably not completely quiet for all of those 60 nanoseconds. So, again assuming, that small groups rely on getting the bullet to exit the muzzle within a very short time window - something on the order of 10's of nanoseconds.

For a frame of reference, with the barrel time of bullets around a millisecond, the sound wave would travel back and forth from the breach to the muzzle about 20 thousand times before the bullet is at the muzzle.

For me, I can get seating depth is directly related to the time the bullet gets to the muzzle. What seems complex is why accuracy nodes tend to be so far apart in terms of powder charge. And, how accuracy nodes can span a couple tenths of a grain.

 

[PigButtons]

Just a thought when reading Damon's post. By the way, thanks Damon. What if each of the flutes were of a distinctly different length, just for the sake of discussion say 1 inch increments. Would that yield some frequency cancellation? and would that be helpful?

And of course is is like Edd above so clearly relayed the wisdom: you just have to test it.

 

[gunsandgunsmithing]

IMO, managing inevitable vibration is the best approach to accuracy. While dampening can and does have its role, it's way down the list of importance. That why all tuners will tune a barrel but some do it better. Dampening is important but it's not what we use to tune.

 

[dcali]

Just a thought when reading Damon's post. By the way, thanks Damon. What if each of the flutes were of a distinctly different length, just for the sake of discussion say 1 inch increments. Would that yield some frequency cancellation? and would that be helpful?

And of course is is like Edd above so clearly relayed the wisdom: you just have to test it.

Using non uniform flutes would change both the frequency of the modes and the shapes - you’d be vibrating an asymmetrical beam, I suspect it would make things worse if not done very carefully and purposefully, but who knows. Maybe there’s a clever way to get it to cancel something out.

 

[dryhumor]

Most fluted barrels are not fluted the entire length, seems that changing the depth, length, and number would accordingly change the resonance. And what degree of change or non change would be there if flutes extended onto the neck, shoulder, or chamber area of a barrel. Or all the way to the muzzle.

As to fluted and stiffness, a flute is an inverted arch, of X degrees in the belly of the radius. Arches are pretty robust. Wouldn’t a duel radius flute scheme be stiffer. The same radius both above and below a mid line composed of true arches that support each other the circumference of the barrel.

Thinking out loud.

 

[mensajd]

Fluting is interesting and does have weight benefits. But it is another machining step that adds to the tolerance stacking. Are the flutes identical and perfectly symmetrical about the bore axis? Was the barrel sufficiently stress relieved such that the barrel material is uniformly isotropic? Fluting has its place but empirical observation suggests that it is not employed in ultimate precision/ accuracy disciplines.

 

[joshb]

Just spent the time to read thru this thread. Thank you guys. This is what makes this forum shine.

 

[TAJ45]

Just spent the time to read thru this thread. Thank you guys. This is what makes this forum shine.

I have enjoyed it as well. But I must admit that I need a Tylenol or two.....

 

[dave@aDave]

A very good thread.
Two observations:
1. "If you can't explain it with numbers, you don't understand it" - Lord Rutherford, a practical experimenter
2. "You do not really understand something unless you can explain it to your Grandmother" - Albert Einstein, a theoretical physicist

Now a corollary for the above that relates to accurate shooting:
It is better to proceed with a good idea than to wait until you have all the answers" - Admiral H. Rickover, engineer

 

[davidjoe]

Fluting is interesting and does have weight benefits. But it is another machining step that adds to the tolerance stacking. Are the flutes identical and perfectly symmetrical about the bore axis? Was the barrel sufficiently stress relieved such that the barrel material is uniformly isotropic? Fluting has its place but empirical observation suggests that it is not employed in ultimate precision/ accuracy disciplines.

Some guys would say any additional steps beyond a cleaned up 1.25 straight contour can only decrease accuracy. There’s an interesting company doing much more than fluting to very large diameter barrels.

They discuss on their website huge gains in harmonic deadening and stiffness for weight. They deep hole drill these barrels around the central rifled bore, revolver cylinder style, as well as employing a number of other operations down the length.

They support their theories with explanation. Their data includes demonstrations of these big rifles in action and it is definitely a good watch.

 

[dcali]

Some guys would say any additional steps beyond a cleaned up 1.25 straight contour can only decrease accuracy. There’s an interesting company doing much more than fluting to very large diameter barrels.

They discuss on their website huge gains in harmonic deadening and stiffness for weight. They deep hole drill these barrels around the central rifled bore, revolver cylinder style, as well as employing a number of other operations down the length.

They support their theories with explanation. Their data includes demonstrations of these big rifles in action and it is definitely a good watch.


View attachment 1191066

This looks like a lot of hand-waving to me. All they've really accomplished is making an extremely expensive barrel with convoluted fluting. "Harmonically dead" is meaningless marketing speak, and the explanations they give for how it works are largely just flat-out wrong.

 

[dcali]

Speaking of stuff that's wrong, pay no heed whatsoever to Bill Calfee's "stopped barrel" theories. It's absolutely incorrect. So incorrect that you can't even argue against it. It's just plain not how physics work.

 

[butchlambert]

Fluting is interesting and does have weight benefits. But it is another machining step that adds to the tolerance stacking. Are the flutes identical and perfectly symmetrical about the bore axis? Was the barrel sufficiently stress relieved such that the barrel material is uniformly isotropic? Fluting has its place but empirical observation suggests that it is not employed in ultimate precision/ accuracy disciplines.

Most of you are relatively new to BR shooting. Back in the dinosaur age a BR shooter and smith named Skip Otto made a lot of money fluting barrels. Skip had a very large horizontal mill. Skip would mount 4 barrels on the bed. I don't remember if he had them tied to a linked chain, but they all indexed at once.
Oh, I was in Phoenix when he set the World Record at that time a .099" group at 200yds. Skip only fluted barrels. Maybe it would have been an .060" if it wasn't fluted.

 

[hpshooter]

"Oh, I was in Phoenix when he set the World Record at that time a .099" group at 200yds. Skip only fluted barrels. Maybe it would have been an .060" if it wasn't fluted."

In the 60's there was a smith named Seitz in the Lexington VA area that fluted a lot of barrels. I did not know the gentleman but a couple co-workers bought light weight hunting rifles from him. They made the typical claim that the fluting made the barrels stronger, their explanation boiled down to that is what they were told. Their standard of accuracy was minute of deer. Don't know if he built target or varmint rifles. He may have built some superbly accurate pieces for the time. If so, I would guess it was due to meticulous fitting, chambering and bedding (as Skip Otto did) and not the fluting. My opinion only it is worth what it cost you!

 

[davidjoe]

Should I cancel my order of 6?

I actually do have a straight 2 inch barreled .408 cheytac but I wouldn’t want to cut it up.

Their barrels likely do group well, but my take is that when you have that much steel, it would be very hard to produce a barrel that wouldn’t group well.

I shoot matches from .22 LR on up and sheer mass does have something positive to do with good results. I think we subconsciously all know this to be true which is why in big matches the weight limit is not a flexible concept and there are no exceptions.

 

[mensajd]

Speaking of stuff that's wrong, pay no heed whatsoever to Bill Calfee's "stopped barrel" theories. It's absolutely incorrect. So incorrect that you can't even argue against it. It's just plain not how physics work.

LOL! In math/physics circles, we refer to this type of theory as "not even wrong" [paraphrased] or "Das ist nicht nur nicht richtig; es ist nicht einmal falsch!" Usually attributed to physicist Wolfgang Pauli.

 

[dcali]

LOL! In math/physics circles, we refer to this type of theory as "not even wrong" [paraphrased] or "Das ist nicht nur nicht richtig; es ist nicht einmal falsch!" Usually attributed to physicist Wolfgang Pauli.

I hadn't heard that one! I'll haae to keep it in mind. Comes up from time to time.