Fluted Barrel Heat Dissipation?

[Picher]

I have a Fluted, Rem 700 Light Varmint .223 Rem and recently noticed that when the barrel heats, the flute grooves seem cooler than the ridges. I had always touched the ridges to check for barrel heat, but thought the grooves would be hotter because they're closer to the bore.

Has anyone noticed that besides me, or can explain the science behind it?

JP

[Art Eatman]

Thinner metal cools faster, probably. About all I remember from my heat transfer, fifty+ years back, is that heat loss is a fourth order function.

[PatientWolf]

I could certainly be wrong, but I would be very surprised if you actually were able to feel the difference in the temperature in the grooves vs the temperature on the ridges of the fluting. The heat transfer of the metal should be such that the temperature is pretty close to the same in both areas. In theory, the fluted barrel may cool faster than a non-fluted barrel due to the additional exposed surface area created by the structure.

But then again it has been a few years since I had my heat transfer and materials theory classes and of course they were theory-based with limited practical labs.

[FrankenMauser]

Polished ridges and bead-blasted flutes?

[Reloadron]

I recently did a small science experiment on barrel heat. It was actually more about primers but barrel heat figured into things. I measured the barrel surface temperature just forward of the chamber. I was shooting 223 Remington in a custom version of an old Remington 725 re barreled with a heavy fluted 1:12 barrel. Ambient temperature was about 73 degrees F. The setup is pictured below:


Rifle with temp sensor secured with Kapton tape:


On average i fired one shot every 45 to 60 seconds. After ten shots the barrel was in the mid 90s (right around 95.5 Degrees F. It never went above that as I continued to fire one round every 45 to 60 seconds. All in all for the primer experiment I shot 40 round all identical loads with only the primers changing.

Ron

[T. O'Heir]

Fluting is nearly 100% purely decorative. However, the theory is that increased surface area will increase heat dissipation. That does work with fins like those on a Thompson SMG. Fins are the same as the heat sink(s) on a computer's CPU(And that is not the box!). Fluting doesn't do much of anything.
Like PatientWolf says, you couldn't tell any temperature difference just by touching the barrel.

[jmr40]

Fluting is nearly 100% purely decorative.

On full auto military weapons it can make a difference in heat. On a sporting rifle the difference is probably more theoretical than practical.

The main advantage for most hunters or target shooters is to reduce weight while retaining barrel stiffness. It is still a compromise. A standard contour barrel that is fluted won't be quite as light as as a much thinner featherweight or mountain rifle barrel. Nor will it be quite as stiff as an unfluted standard barrel. But if done right I think they can be a good compromise between accuracy and light weight.

[Picher]

Both flutes and ridges seem to be equally finished...non-glare.

At the bench, I often monitor barrel temperature to keep accuracy consistent and prevent premature accuracy reduction. When it feels hot to the touch, I allow more cooling time between shots.

[hooligan1]

I have a fluted barrel on my Turk, 6.5-06.
Not purely for decoration, as Jmr40 pointed out it lightens rifle barrel by some, and helps create more surface for cooling and rigidity.
I had a Savage 110 .270 win that I would continue to shoot after barrel go too hot to touch, ruined that barrel.
Now if it's going to be in the 90's, this little piggy stays home from the range, because 15 min firing sequences and barrel cool down periods don't mix for me. ( I use a public 100 yd range here not far from my house).
I can't calculate how much differences are made by having fluted barrels, I do know this is a sweetie pie, so I don't shoot it when it gets hot.

[mapsjanhere]

As you're heating from the center out the temperature in the groove will always be higher than on top of the fin, especially in a poor hear conductor like steel. But even with a decent conductor like aluminum you quickly run into transfer limits, which is why you don't see aluminum engine blocks with more than a couple inches of fins. Been a long time but we had to calculate at which length you would melt the aluminum at the base of the fin before you got the tip to get hotter, was less than 4" as I recall.

[5whiskey]

The main advantage for most hunters or target shooters is to reduce weight while retaining barrel stiffness. It is still a compromise. A standard contour barrel that is fluted won't be quite as light as as a much thinner featherweight or mountain rifle barrel. Nor will it be quite as stiff as an unfluted standard barrel. But if done right I think they can be a good compromise between accuracy and light weight.

This is really the main purpose of a fluted barrel. Technically there is more surface area, so technically it should cool slightly faster. There is no practical difference. There is a practical weight savings, while still allowing one to have a varmint or target contoured barrel

[HiBC]

Assume two identical barrel contours,one fluted,one not.

For the moment,lets consider heating and cooling as separate processes.

For the process of rapid fire heating up,the unfluted barrel will heat up more slowly because it has more mass.

The heat from 100 rounds over a given time will heat a 4 lb barrel hotter than a 5 lb barrel.

However,cooling IS part of the equation.A fluted barrel ,with more surface area will cool somewhat quicker.

Testing is the proof,of course,but with the common fluted sporting barrel I don't think you will see a dramatic change in cooling rate.

Just a guess on my part,I suspect over the course of shooting a string of 10 or 30 rounds the heavier barrel mass will moderate temp more than the accelerated cooling of a fluted barrel.

I suspect the reason the ridges felt hotter than the valleys is that your skin had more contact pressure on the ridges,so the heat transfer was more rapid.

But I could be wrong.

[Picher]

I think there is a difference in retained temp between the grooves and fins. One factor we don't think about is that the grooves have less mass than the fins, so they may transfer heat to the fins, to the outside air, and to the air inside the bore.

The fins have greater mass, so probably retain heat longer.

For best accuracy in centerfire rifles, I'm convinced that round barrels have greater potential to be more accurate, especially when shooting long strings. They're just not as attractive to most people.

[TXAZ]

Fluting is nearly 100% purely decorative.

Not true. Look at electronic thermal sinks. They're the difference in electronic items operating in warm to hot environments or not.

And their "fluting" may be more intense than a barrel but added surface area increases both convection and radiated energy.

There are many books on thermal management that bare that out.

[Scorch]

We calculated it out one time, the surface area increases about 20% on a heavy barrel with 6 flutes, less on a lighter barrel because the flutes are shallower and there is less surface area to begin with. You are losing mass as well because you are removing metal. So yes, the barrel will cool faster, even though steel is not particularly good at moving heat. The barrel will also heat faster, since there is less metal in a fluted barrel. So, bottom line, there is not a lot of gain. You can flute to lighten a barrel. You can flute to increase cooling, but people do not let their barrels heat up to the point of being too hot to touch (cooling effect increases with difference in temperature). You can do it for aesthetics. Whatever reason you choose, it makes money for the machinist and does little for your rifle besides make it look different. But hey, if that's OK with you, it's OK with me.

[dakota.potts]

I'm not a physics major but I do know just a little bit about metals and how they handle heat (and I do mean just a little bit)

A heavier barrel versus a fluted barrel should have slightly more mass and therefore should heat up more slowly. As far as heat dissipation, I do think there's a theoretical advantage of increased surface area allowing ambient cooling to happen faster, but metal returns to ambient temperature very slowly in my experience. Maybe there's more of an advantage in a forced cooling environment such as cycling air.

I do wonder if there's any utility in finishes such as Nitride which reduce friction and provide better heat dissipation. Might be another avenue to look at for somebody who's concerned about it. It seems to work out pretty well for steel machine tooling.

[mapsjanhere]

Look at electronic thermal sinks

They only work due to forced convection in most cases, as everybody who had a fan failure on their computer found out. Few people seem to combine their fluted barrels with cooling fans, maybe it's a market niche to explore.