FLUTED BARRELS - GOOD OR BAD

[Hkbeltfed]

Then..FIN that bitch & we'd be GTG.
Ive argued with people to the point of near fisticuffs that a fluted barrel is NOT "stiffer" than an otherwise un-fluted one. I got to where I just say "ok then".

A similar barrel unfluted? Or a barrel of the same weight as the fluted one?

[Straight Shooter]

A similar barrel unfluted? Or a barrel of the same weight as the fluted one?

I was joking...not a fan of ANY of that.

[ScottsBad]

One other aspect, thermal radiation keeps working even when the surrounding air achieves equilibrium, etc.

Now if someone could just explain why black radiates better, never figured that out.

In any case, I agree... weight/stiffness is the real reason fluting matters for all but bench rest types.

I never bothered looking into why black radiates and absorbs better than white does on my own. An assignment or lecture 20+ years ago probably explained it. I never cared enough to explore that on my own though.

Black also absorbs better. There is a clue there.

White reflect all wavelengths. Black absorbs all wavelengths. Black is more closely coupled to the electromagnetic field, in other words black is more conducive to the transfer or conversion of thermo electric energy given off by atoms in an excited state. Colors that are good absorbers are good emitters too.

BTW - Why does this thread just keep going around and around? The facts were known back 20 some odd posts ago.

[pinzgauer]

Black also absorbs better. There is a clue there.

White reflect all wavelengths. Black absorbs all wavelengths. Black is more closely coupled to the electromagnetic field, in other words black is more conducive to the transfer or conversion of thermo electric energy given off by atoms in an excited state. Colors that are good absorbers are good emitters too.

Yep, we all know that black absorbs better and white reflects better, etc. Still does not address *why* they are better radiators, and I'm not sure "more closely coupled to EM fields" explains why.

Found the non-snarky answer: The amount of energy a body absorbs and that which it reflects has to sum to 1. So the more it reflects, the less it radiates, and vice versa. Still not exactly "why", but is a physical law that governs it.

The "why" turns out to be that elements that are more likely to absorb photons raise their energy levels show as black when at thermal equilibrium due to that characteristic. Not the other way around. And that characteristic is bidirectional, they also more easily will radiate a photon to drop the energy level. That characteristic may be "more closely coupled to EM fields", but the real reason is their atomic structure.

Also, color and emissivity are two different things! You can have black items glow red at higher energy levels. It's the atomic structure which matters most, apparently.

[tom12.7]

So I made the stretch to contact someone who actually works in this field.
The reply was almost a 10 page return of citations of sources with links to sources that are used that are not 2 lines long to begin with. Looks over 20K long in total pages with illustrations.
I have little desire to delve into those details with normal time restraints.

[tom12.7]

Per an email, the info isn't secret by any means. Just a login to most any university to actually see them. It's not a secret, just secured by them. Just login with your username and passcode. The citations are open to view if you desire to look at them.

[MegademiC]

I always just thought it was that the black coating absorbed the heat better, which will lead to better radiation... since the steel isn't black. The barrel itself isn't radiating anything, it's the surface.

That's assuming the same surface. If you are comparing a 416stainlessnsurface to a bar of 4150 with a phosphate coating, we are talking a few variables at play.

If you have an anodized surface, does black still radiate better than an un-dyed surface?

[Ned Christiansen]

I did a study on this many years ago using lengths of 1" round steel, all the same length, capped with Transite insulating material on the ends so only the "diiferent" areas would be tested: fluted and unfluted versions of painted, unpainted, blasted, polished. I used an IR pyrometer.... what with it not being a lab-grade test, and as I have not seen the spread sheet in 3-4-5 years, I won't try to cite results other than this: polished vs/ blasted was quite a dif as expected. It said so right in the Machinery's Handbook-- polished surfaces tend to not want to be affected by ambient temp. Part of my reason for testing was that I was sure a spray and baked surface would act as an insulative barrier that would more than offset the tendency for black to radiate better. It still did cool faster although I remain convinced that a really thick coating would impede cooling.

I have fluted many barrels to a pretty radical level. Most factory fluting is so lawyerishly shallow as to qualify as decoration only. Several that I've done were for a High Master shooter in NRA High Power who reported in every case, no accuracy degradation. I do it in such a way that I believe any cutter-induced stresses are minimized, although I can't claim it as a proven fact.....

[ScottsBad]

Yep, we all know that black absorbs better and white reflects better, etc. Still does not address *why* they are better radiators, and I'm not sure "more closely coupled to EM fields" explains why.

Found the non-snarky answer: The amount of energy a body absorbs and that which it reflects has to sum to 1. So the more it reflects, the less it radiates, and vice versa. Still not exactly "why", but is a physical law that governs it.

The "why" turns out to be that elements that are more likely to absorb photons raise their energy levels show as black when at thermal equilibrium due to that characteristic. Not the other way around. And that characteristic is bidirectional, they also more easily will radiate a photon to drop the energy level. That characteristic may be "more closely coupled to EM fields", but the real reason is their atomic structure.

Also, color and emissivity are two different things! You can have black items glow red at higher energy levels. It's the atomic structure which matters most, apparently.

Are you guys being obtuse on purpose?

I explained it as simply as possible, of course there's more to it. If you want to know the details just look it up. BTW - You said you don't understand why radiant energy (heat) is still radiated even when the barrel and air reach equilibrium? At least I think that's how you stated it. IN SIMPLE TERMS; The reason is that atoms/molecules in an excited state will throw off photons in a spectrum that we feel as heat. That is the red you see when extreme heat is applied [some photons are created in the visible light spectrum too]. So as not to have you tell me that doesn't explain it, the simple answer is that air molecules do not present a barrier to photons. What state do they have to be in for this to occur and what is the exact mechanism? I'm not going to try to explain why, frankly I can't remember exactly, if you want to know look it up.

The "why" turns out to be that elements that are more likely to absorb photons raise their energy levels show as black when at thermal equilibrium due to that characteristic. Not the other way around. And that characteristic is bidirectional, they also more easily will radiate a photon to drop the energy level. That characteristic may be "more closely coupled to EM fields", but the real reason is their atomic structure.

Oh , you are so smart since you went and looked it up. You don't have it quite right, but I'm not going to spend a lot of time correcting you. It not that its the other way around, its both ways. The coating absorbs all visible (to us) spectrum and appears black, its black because it absorbs all visible spectrum.

Just because you didn't understand the implications in my simple description, doesn't mean I'm wrong. It mean that you couldn't intuit the ramifications. There are always details to learn, but its easy enough to look them up.

I already gave you a clue about radiant heat above.

Also, color and emissivity are two different things! You can have black items glow red at higher energy levels. It's the atomic structure which matters most apparently.

I don't know where you are going with this....Jesus.

[0uTkAsT]

I found out earlier this year that BCM does not recommend using suppressors on their ELW-F barrels. They say to go with the regular ELW barrels instead. This must have to do with the rigidity component, I'm assuming. Thought it was worth mentioning in here because I never thought mild fluting would make much difference in a barrel one way or another, surface area aside.