Nodes?

[Snakeoil]

Like everything else, every hobby, profession, diversion has its own language. I have read several posts here trying to improve my knowledge on the subject. I noticed the term "node" or "nodes" being used. What I've gleaned from reading the posts is it appears a node is a sweet spot where bullet speed, type, powder charge, seating depth and rifle all play well together and produce and excellent group. But it also appears that node relates to balance of the bullet as it spins like the harmonics in a spinning shaft produce different distortions at critical speeds.

Is there an good explanation of "nodes" relative to cast bullet shooting or just shooting I can read. I don't like to ask folks to explain stuff to me that is readily available to the reader. I did a search, but obviously it results in lots of posts where node was used in a discussion, with the definitions assumed to be a given.

Thanks.

 

[Snakeoil]

Never mind. I found some good stuff. I'll post links here as I imagine others may have the same question in the future.

 

[Ian]

Here: https://www.artfulbullet.com/index.php?threads/article-8-barrel-harmonics.185/

 

[Snakeoil]

Thanks. Here is one I found.

RSI - General Reloading Tips

Barrel Harmonics, Timing & Theory

www.shootingsoftware.com

 

[Ian]

I linked RSI at the end of the article. Good stuff.

 

[Snakeoil]

Your summary did a great job of boiling it down. They only loads I have ever worked up were BP loads for my Shiloh. So powder choice was pretty limited. And I suspect I got lucky and found a load the rifle liked early in the game. So, this should be fun... I think.

 

[Pistolero]

Also, those huge octagonal bbls on the Sharps are VERY stiff, so they are less prone to the vibrations that make
the difference.

The stiffness coefficient for a round bar in bending (an octagonal bbl is going to be even
a little bit more stiff than round the same diam) is a fourth power function of the diameter.

So if we take the the bending stiffness of a 0.550 solid bar as 1.0 "Units of stiffness", a 1" diam solid bar
would have a stiffness of a hair under 11.0 "units of stiffness". The holes make a difference, but the comparison
is still valid.

Your experience working with a 1" bbl will not let you see anywhere near as much vibration as a 0.550 sporter
bbl. And also the peak pressure of BP is far lower, so the excitation of the vibration is much less, too.

Bill

 

[462]

Bill,
That may explain why those old black powder buffalo rifles had heavy octagon barrels.

Or, they just may have been easier to manufacture.

 

[Pistolero]

They 'hung' well, heavy is stable, but they also shot well because they were very stiff.

Bill

 

[Bret4207]

It was also believed for a long time that the heavier a barrel, the more accurate it could be and that light barrels were notoriously inaccurate. That hung on until 20-30 years ago IMO.

 

[Ian]

That was probably a lot more true 20-30 years ago, too. Modern steel and manufacturing processes have changed a lot of old truths.

 

[Intheshop]

I don't want to get this thread too far off the rails but......

Rarely is a "bore" straight,a fact that is very well known and adjusted for by top flight smith's in the fitting process. It's a whole lot tougher trying to optimize a factory tube. And is "one",of several reasons folks choose to turn them into tomato stakes and go for a "custom" barrel.

The mistake here,like it is in many sports where the equipment "seems" to be the path to the winner's circle, vs working on the skill side...... is,that there aren't folks out there who manage quite well dialing in factory barrels. Gotta tread lightly here because,spending $$$ on a custom barrel only to get,"put on the trailer" by some huckleberry shooting a factory stick,ain't exactly good for business.

But back to engineering and bent,or not straight barrels.... I was straightening some aluminum arrows this morning. Yes we have the fancy fixtures with dial indicators.... but. When you turn an arrow in your two hands applying thumb pressure you can feel,in no uncertain terms how the "high" side is so much stiffer to push against than it is the low side,pushing it towards.... making it worse.

So,while all the wave tuning is great N all..... the theories are leaving more on the table than folks realize. And is why these bends need to be oriented in the vertical plane.

Another "aspect".... which can be looked at is where the vibrations are being transferred to. Again,can't be rocking the boat too much because there's a lot of smiths making money setting up stocks. Further,not trying to point fingers but..... in general, wood workers are not known for their acceptance of "certain" engineering terms,from a knuckledragging standpoint. So,combine..... "this is how we've always done it" >with< an inflated ego and well,there's an AWFUL lot left on the vibration table through stock misunderstanding.

Mass weight seems to be the "shortcut" taken by most folks in both,barrels AND stocks.

 

[Snakeoil]

The rifle in question in an 03 Spfld with orig 1921 bbl. Not only is it skinny relative to my Shiloh, the machining of the OD was done by a blind man known to have fits. But I like a challenge. Plus I have friends with NRA Sporters and Match Spflds that shoot MOA or better at 100yds, or so they claim.

I understand the node term now. It is not unlike the response of large rotating shafts to changes in RPM. Initially I uad gotten the impression it was rifleman speak for group.