FLUTED BARRELS - GOOD OR BAD

[ScottsBad]

Let's find out what an engineer had to say about barrel fluting. Here is the link to Varmint Al's explanation of how fluting affects barrel stiffness and accuracy
http://varmintal.com/aflut.htm

If the article makes your eyeballs glaze over, here are the Cliff's Notes

From your Cliff's notes, this is the part that explains the differences well:

....Fluting a solid barrel will:

Reduce its weight

Reduce its stiffness

Increase its natural frequency of vibration

Decrease its muzzle sag.

Reducing the weight of a barrel by fluting makes a stiffer barrel than reducing the weight by decreasing its diameter.

A shorter barrel of the same section, solid or fluted, will sag less and vibrate at a higher frequency.

The notes left out cooling, but cooling is a very minor factor because the rate of cooling, even with flutes, is slow compared to the amount and intensity of heat put into the barrel during normal semi-auto shooting. In other words, the increased transfer of heat to to the air is small and slow when compared to the heat going into the barrel from shooting.

I made essentially the same points way back in post #12.

Stickman is right the only practical advantage to fluting is weight reduction. Mistwolf is right when he posts the "Cliff's Notes" about barrel fluting. Barrel vibration (harmonics) is an issue but so are the effects of heating and cooling when the material is not a uniform thickness.

[MegademiC]

What is the temperature capacity radiated from the the inside corner of that said fluting to an outer corner? Something to think about.

As said, the heat loss properties are almost negligible in the real world.
I'm not sure what you mean by "temperature capacity".

The heat loss will be Dependent ultimately on rate of fire and distance of the bottom of flutes from the bore, and bore to OD, and heat capacity of the barrel (probably negligible).

[tom12.7]

Thermal capacity, as in how many BTU's of applied heat to be stored by the barrel before a temperature limit is reached after a resonance time for the base material is considered. Heat transfers from the barrel to the air (ideally). The higher the delta between the air temp and barrel temp, the higher the rate of transfer. The higher the surface area, the higher air can be potentially in contact to transfer that heat. Part of the key is that air needs to flow, we need air exchanges to allow cooler air come in and absorb heat. Fluted barrels act in many ways similar to an air cooled motor without a cooling fan. If you measure the temperature in some different locations, you might get surprised.

[pinzgauer]

Thermal capacity, as in how many BTU's of applied heat to be stored by the barrel before a temperature limit is reached after a resonance time for the base material is considered. Heat transfers from the barrel to the air (ideally). The higher the delta between the air temp and barrel temp, the higher the rate of transfer. The higher the surface area, the higher air can be potentially in contact to transfer that heat. Part of the key is that air needs to flow, we need air exchanges to allow cooler air come in and absorb heat. Fluted barrels act in many ways similar to an air cooled motor without a cooling fan. If you measure the temperature in some different locations, you might get surprised.

That explains conductive heat loss.

There is also heat loss via thermal radiation (infrared rays), which is also dependent on surface area. Unlike conduction, it is not dependent on airflow or exchange.

For humans, the majority of our heat loss is via thermal radiation. You see a figure of 65% quoted quite a bit. Don't know if the % holds for barrels as well, but I conjecture it's similar.

Thermal radiation is how Arizona and Africa can go from 100+ during the day to below freezing at night.

Short version: fluting is a good thing, if you care about accuracy/weight tradeoffs.

[militarymoron]

I'd like a fluted pencil barrel with dimples on the raised flutes; just to cover my bases.

[tom12.7]

That explains conductive heat loss.

There is also heat loss via thermal radiation (infrared rays), which is also dependent on surface area. Unlike conduction, it is not dependent on airflow or exchange.

For humans, the majority of our heat loss is via thermal radiation. You see a figure of 65% quoted quite a bit. Don't know if the % holds for barrels as well, but I conjecture it's similar.

Thermal radiation is how Arizona and Africa can go from 100+ during the day to below freezing at night.

Short version: fluting is a good thing, if you care about accuracy/weight tradeoffs.

I sort of agree on this explanation for this for radiation, but for simplicity I omitted thermal radiation from further posts for the way this discussion was headed.

[pinzgauer]

I sort of agree on this explanation for this for radiation, but for simplicity I omitted thermal radiation from further posts for the way this discussion was headed.

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.

[tom12.7]

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.

[Straight Shooter]

I'd like a fluted pencil barrel with dimples on the raised flutes; just to cover my bases.

Then..FIN that bitch & we'd be GTG.
For me- flutes/dimples/pimples/ect are merely cosmetic ..nothing Id ever need. 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".

[MegademiC]

I sort of agree on this explanation for this for radiation, but for simplicity I omitted thermal radiation from further posts for the way this discussion was headed.

Edited, misread.
As you mentioned, it's heat capacity, not temperature capacity, threw me for a loop.