Stainless barrels and range use?

[Bushleague]

The other day I had a few rifles at the range, a stainless .270 and a 30-06 and a 6.5 with blued barrels. I was surprized at how much more quickly the two blued rifles cooled off. I realise that the .270 might generate a bit more heat than the other two but it seemed to take almost twice as long to cool off. This is pretty much right in line with how stainless behaves when it is welded, just wondering if anyone else has found this with stainless barrels, or if its just a .270 thing.

[Lefty-Canuck]

What was the contour and clambering of each of the barrels?....I think that has more to do with it than the finish on the barrel.

LC

[Bushleague]

Originally Posted by Lefty-Canuck

What was the contour and clambering of each of the barrels?....I think that has more to do with it than the finish on the barrel.

LC

Contour was similar, the 6.5 was a bit heavyer and the 30-06 a little lighter than the .270. The 6.5 cooling off faster makes sense but the difference between the .270 and the 30-06 seemed way bigger than I would have thought.

[RobF]

Black radiates heat better then any other color, paint your stainless barrel black and it would cool off just as quick.

Same reason they use to paint car radiators black.

[bsmitty27]

I'm interested in this one, black absorbs radiant heat better than lighter colors. But we're talking about dispersion. I don't see why it would disperse heat any faster. I'm going too see what google says. (she never lies)
Brad

[j.d.miller]

Originally Posted by bsmitty27

I'm interested in this one, black absorbs radiant heat better than lighter colors. But we're talking about dispersion. I don't see why it would disperse heat any faster. I'm going too see what google says. (she never lies)
Brad

Agree. Dispersion is different and you'd almost think the paint would act as an insulator for the heat genterated inside.

As for the radiator comment... Racing radiators are all aluminium and not painted black.

Any handloads or all factory?

[Leeper]

Though you may not be able to see why black would disipate heat faster, the truth is that it does. Bright silver radiates heat less than anything with white a close second. Painting a set of headers white reduces the temperature under the hood and increases the temperature of the exhaust. Painting a stainless barrel black allows it to radiate heat at a faster rate.
An interesting experiment is to heat up a piece of brightly polished aluminum and try to get a temperature reading with and infra-red heat sensor. You will find the temp reads very low. Now paint it black and try again and you will get a true reading. In spite of the fact that aluminum conducts heat very well, the silver finish reduces radiated heat. You can, quite literally, feel the difference.
I have used both stainless and blued barrels on target rifles and there is no question that the blued barrel cools down more quickly; providing the rifle is in the shade. In the sun, the black finish causes the barrel to absorb heat from the sun much more quickly as well. Leeper

[Full Curl Earl]

Every scientific bone in me says that's incorrect! Lol
Heat created internally wants to be released. Any blueing or coloring will inhibit this. Stainless stays hotter longer because its molecularly a tighter packed steel, which is why Aluminum, a loose molecular product cools much quicker. If you were to coat the stainless in anything, it would increase its cool down time.
Dark colors conduct heat faster, but that's the only color relevance to heat. Unless there is some new super paint out there that controls heat dispesion? Then they can start painting all rockets black for re-entry, and engine blocks will all be black as well.

[Full Curl Earl]

The temperature read issue has to do with the device reading the product, i am certain that an actual contact sensor would have read otherwise.
Definately an interesting topic.

[Bergerboy]

The two different materials have different thermal conduction properties. I looked up Lilja Barrels and they use 4140 chromoly and 416 stainless for their bar stock. If you compare the nominal thermal conductivity of each the 4140 barrel is 42.7 W/m-K (watts per meter kelvin) and the 416 is at 24.9 W/m-K. With the application of Fourier's Law of conduction, the chromoly barrel should cool down 1.71 times faster. I think this would account for most of the difference.

[Leeper]

Full curl earl,
Of course a contact sensor would have read differently. A contact sensor would read material temperature while the IR sensor reads radiated heat and is fooled because of the bright finish. The influence of colour on heat radiation is demonstrable and is taught in elementary school science classes.
FWIW, bluing has no dimension whatsoever and therefor, no insulating properties. Leeper

[Leeper]

Although colour influences heat radiation and this is indeed demonstrable, virtually every bit of scientific data I have read indicates that the colour has less effect than does the surface finish. In other words, a matte gray, sandblasted, finish is more effective at dissipating heat than is a shiny black one and ultimately, although there is a huge difference in infra red radiation, there is little difference in heat dssipation since the radient component is insignificant compared to heat loss via convection. I, as it turns out, was wrong to have thought the effect was greater than it really is. It may well be that Bergerboy is correct in his statement that it is the conductivity of the two materials which accounts for the perceived difference in cooling and not the colour.
As you can see, an old dog can learn. I think it is important to note, however, that a dumb dog cannot. Leeper

[Bergerboy]

Leeper is correct in saying color does affect the cooling rate. Planck's Law shows that through spectral radiance black barrels emit radiation at a much higher frequency than a white barrel. The higher the frequency the faster the transmission rate. A fellow posted above that race car radiators are not pained and they have superior cooling properties. This is true but only because they are made of aluminum which transfers heat 4.8 times that of steel (205 W/m-K).

[Full Curl Earl]

Beg to differ, but that's ok.
-Blueing is certainly measurable.
-IR heat was not in question, "real" heat diss. was the query.
-Your elementary school was obviously leaps and bounds above mine, thermal dynamics wasn't really getting underway until Junior High.
So my question is this, if I were to heat 2 identical stainless barrels, to the exact same temp measured inside the tube, and one is painted white and the other black, in a sealed unlit environment, would both barrels cool equally?

And so the OP is clear, the material has way more effect than the science lesson being crushed here. I have found that stainless material takes longer to cool than carbon, fluting pretty much overcomes that issue in my opinion.
Why the dumb old dog comment? I don't get people name calling folks on here.
Fun talk!

[Bergerboy]

Originally Posted by Full Curl Earl

Beg to differ, but that's ok.
-Blueing is certainly measurable.
-IR heat was not in question, "real" heat diss. was the query.
-Your elementary school was obviously leaps and bounds above mine, thermal dynamics wasn't really getting underway until Junior High.
So my question is this, if I were to heat 2 identical stainless barrels, to the exact same temp measured inside the tube, and one is painted white and the other black, in a sealed unlit environment, would both barrels cool equally?

And so the OP is clear, the material has way more effect than the science lesson being crushed here. I have found that stainless material takes longer to cool than carbon, fluting pretty much overcomes that issue in my opinion.
Fun talk!

Believe it or not heat dissipation is IR and both are real. Now to answer your question. Yes. If you exposed two barrels of the same material to the same temperature and not exposed to light, the one painted black would cool faster. A fluted SS barrel would cool at the same rate if the surface area / unit mass was 1.71 times higher than a cromoly one. As per bluing you claim "Bluing is certainly measurable" it is 2.5 microns or 0.0001" thick. You got some badass calipers. For that thickness it will not have insulating properties.

[Full Curl Earl]

Never doubted the existence of IR or heat diss, lol.
Your selfless dedication to your fellow sportsman is indeed inspiring. Thank you for showing your work...
Yes calipers..
The thickness of the blueing, which varies greatly, is not as relevant as an insulator as it is a barrier to natural convection properties. But I am open to being incorrect, and certain you will attempt to show this.
The topic was not started to have a sword fight, but to see what theories and science was out there.

[Bergerboy]

If you want we can explore the thermal conductivity of bluing. Make sure you have your lunch money ready, I'm hungry.

[Leeper]

To clarify, rust bluing is measurable although it probably does not add significant dimension. Hot bluing might be measurable as regards the depth of the colour but adds no dimension. A one inch guage block which is blued still mikes one inch.
Even amongst those who are much better schooled in thermodynamics than we are, there seems to be considerable disagreement on the subject vis a vis the effect of colour.
One thing I notice is a whole bunch of computer modeling and a a lot of mathmatical computation but very little in the way of hard data from controlled experimentation. I like real world results. Leeper

[Bergerboy]

Originally Posted by Leeper

To clarify, rust bluing is measurable although it probably does not add significant dimension. Hot bluing might be measurable as regards the depth of the colour but adds no dimension. A one inch guage block which is blued still mikes one inch.
Even amongst those who are much better schooled in thermodynamics than we are, there seems to be considerable disagreement on the subject vis a vis the effect of colour.
One thing I notice is a whole bunch of computer modeling and a a lot of mathmatical computation but very little in the way of hard data from controlled experimentation. I like real world results. Leeper

I agree, a real world test would be neat to compare to the theoretical results.

[nekred]

Thermodynamics is a huge field....

look up albedo which is a measure of how much IR radiation is absorbed as compoared to what is reflected....

Look up black body as well which is a measure of how well a material emits IR Radiation....

Take an IR thermometer which measures emitted heat.... and at the same temperature (with contact thermometer) two different materials will measure different temperatures.... Take that IR thermometer and point at the sky and see what you measure.... (not at sun or you will wreck it)....

There are a few things which affect temparature there is radiation, convection and conduction. With two barrells of different colours but made of same material and same density, in the same location in the shade the one that will cool faster all other factors remaining the same is the one with the lower albedo. (less white more black)

But many other factors can come into play... if one is contacted with a cooler surface... say different stck... that conducts the heat away from the barrel quicker because it can radiate the heat more quickly... like cooling fins on a motor....increases surface area for conduction/convection to air...

Now here is another example..... Metal is a great heat conductor.... have a piece of metal in -40 weather and a piece of plastic... at -40 they are same temperature but when you pick one up one feels warmer than the other.... because the metal conducts heat very quickly from your hand....

Now take a black seat in the sun and a white seat... which one gets hotter.... the black seat heats up more quickly because it absorbs more IR quicker.... but the white seat will absorb IR less wuickly but also dissipates it less quickly too.... With heat there is always a balance as it is true Kinetic energy in that it cannot be stored.

So back to the black seat in a car with rolled up windows. The black seat heats up very quickly and saturates the area around and overloads take away capacity which is determined by the thermodynaimc differental. (convection/conduction/radiation) so incoming energy is being radiated as fast as it is coming in thus the black seat is absorbing more energy then re-distributing it including re-radiation which makes it hotter.

The white seat reflects mopre enery away initially, re-radiates less and does not sutrate the system with as much heat as thermodynsmic differential is lower thus does not get as hot, but takes longer to cool down....

This why snow covered field does not melt as quickly as a field with a few black spots showing up in it.....

Paint is extremely important for IR masking as shown by development in Stealthy aircraft....

[Bushleague]

Originally Posted by Bergerboy

The two different materials have different thermal conduction properties. I looked up Lilja Barrels and they use 4140 chromoly and 416 stainless for their bar stock. If you compare the nominal thermal conductivity of each the 4140 barrel is 42.7 W/m-K (watts per meter kelvin) and the 416 is at 24.9 W/m-K. With the application of Fourier's Law of conduction, the chromoly barrel should cool down 1.71 times faster. I think this would account for most of the difference.

And that, right there, is what I'm talking about. From welding school I remember that stainless steel's thermal conductivity is less than that of carbon steel. From welding stainless steel I also know that the warping or pulling that will happen in carbon steel soon after welding happens much later in stainless. I also know that it heats up hotter much faster, I've seen stainless get too hot to comfortably touch just from wire wheeling paint, or taking a light shave off of it with a lathe, while carbon steel will merely get warm to the touch. Hows that for real world tests?

The black verses shiny finish argument, I was under the impression that black ABSORBED more heat because it either absorbs all colors of light, rather than reflecting any of it as other colors do, as for radiating heat I don't really know other than that there is a lot of info that I consider to be highly suspect being thrown around here. An interesting FYI, IR thermometers and even expensive thermal imaging cameras will have enough variation when reading different types of surfaces that the mill where I work requires that we use temp sticks when heating bearings and hubs for fit up. They did a side by side comparison, I cant remember the exact specifics of whether the IR stuff was reading high or low on your typical reflective shaft, but I do know that they decided to change the rules as a result.