carbon fiber barrel

You are going to eat some crow on the concept, but I don't know how easy it will be for your friend to get his dream barrel made for him.

There is no reason the rifling will break down any faster in barrel that has been turned down, than one left in it's original strait blank form. It will make no difference to the bore how much metal surrounds it beyond what is needed for withstanding chamber and bore pressure.

Christensen Arms makes custom rifles with carbon fiber wrapped barrels and they are apparently very accurate. You get all the benefits of a bull barrel without the weight. Carbon fiber is extremely stiff, and is not affected by heat or cold so the barrel will not walk shots when it gets hot. They apparently shoot to point of zero regardless of temp.

I can not speak for the material dissipating heat any more quickly, but given it's lighter weight and lower density it stands to reason that it would.

For further reference.

http://www.christensenarms.com/

I just looked at Christensen Arm's site. They offer both a re-barreling service with Shilen barrels wrapped in carbon fiber, and a service where they will turn down your current barrel and wrap it.

As long as the job is well done, I see no reason not to have this done other than cost. Shilen barrels are very well known for excellent accuracy, and Christensen promises that their custom grade rifles barreled with these carbon fiber barrels with shoot into 1/2 MOA.

The CF is just for weight reduction. CF is actually very bad for heat dissipation. When I raced motorcycles the idea of a CF crank and transmission case was thought about because of the weight but the heat was trapped and caused lots of problems. So aluminum (or magnesium) are still the materials of choice.

The CF is just for weight reduction. CF is actually very bad for heat dissipation. When I raced motorcycles the idea of a CF crank and transmission case was thought about because of the weight but the heat was trapped and caused lots of problems. So aluminum (or magnesium) are still the materials of choice.

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This topic was under debate someplace I frequent a while ago. Lots of physics geeks and engineers went back and forth. Turns out CF conducts heat pretty well. What it is not so hot at is radiating heat.

But with a tensioned sleeve of CF, you apparantly get the barrel heated up fairly evenly, helping reduce distortion due to heat.

As long as it remains accurate across a variety of temps, the fact the CF saturates with heat doesn't matter.

Totally different matter in an engine though.

If a proper machinist turns the barrel, no problems whatsoever.

Carbon fiber dissipates heat amazingly fast. I used to heat up my HMR barrels fairly fast until I put a VQ barrel on, it takes a LOT to get it warm.

I know one issue I've heard of with machining flutes into a heavy barrel is that the mill work might change the size of the bore slightly. That's why they cut the flutes, then bore/ream so I've heard. I would think the same would apply to the above mentioned procedure. Wouldn't it be better to turn it to size first, then bore/ream, then apply the carbon fiber wrap?

no it won't hurt barrel life, it will actually HELP barrel life as it will keep it from getting to hot.

When a barrel is machined how much metal do you think is left? nothing but the rifling? How long have you shot and how much ammo have you put through a barrel, did it wear out the rifling to the extant that it was a smooth bore? On the 22's that I have seen done this way there is almost 1/8" of steel wrapping the rifling, even on a 300 win mag that is more than enough surface area to never wear through. Wrap it in carbon fiber which is STRONGER than steel, no warpage.

again, if it is done by a competent machinist there will be no problems. It is change, and it is a good change for those that want a lighter barrel that will cool amazingly fast.

Carbon fiber dissipates heat amazingly fast. I used to heat up my HMR barrels fairly fast until I put a VQ barrel on, it takes a LOT to get it warm.

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Actually this is a misnomer. Your steel barrels got hot fast because they absorbed the heat from shooting much faster as metal is a better conductor of heat. Materials that conduct heat very well also give it up very well. Pick up a hot wood block and a hot steel block at identical temperatures. Which one feels hotter initially? The steel block, because it absorbs, and subsequently dissipates heat much faster than wood, which is a poor thermal conductor.

A material with poorer heat conduction will absorb heat at a slower rate, giving the illusion that it is somehow dissipating better than steel because it isn't as hot. To take things to an extreme, wrap your barrel in asbestos and it'll take forever to heat up. Does that mean asbestos dissipates heat amazingly fast? No, it's just poor at absorbing heat, and its poor at giving it up. If your heat sink doesn't feel warm at all, you've got big problems. You want your heat sink to be hot.

Anyone familiar with high end camping gear and has played with aluminum, titanium, and steel cookware can attest to this. Titanium is a terrible conductor of heat. Aluminum is one of the best conductors of heat. Titanium takes longer to heat up, but it also retains heat longer. Aluminum is an excellent conductor and heats up very fast, but also cools off very quickly.

There are three types of heat dissipation: radiation, convection, conduction. Radiation of heat is based on emissivity and reflectivity, and doesn't play a massive role here.

For conduction, carbon fiber has poor thermal conductivity compared to steel (though its much better than many other materials). Metals across the board are going to be much better thermal conductors 99% of the case. That is why heat sinks are usually made of aluminum or copper. There are exceptions to this general trend, but they don't concern us in this discussion. Keep in mind carbon fiber are strands of carbon thread suspended in an epoxy binder. Epoxy isn't the most thermally conductive material, and carbon fiber was never designed to be. Have you ever seen carbon fiber products specifically designed as heat sinks?

Convection is simply what it sounds like, using a liquid medium (in our case, air) flowing and carrying off excess heat. This can be natural (setting up convection currents on a static heat source) or forced, like air-forced cooling. This is why heat sinks have fins--to increase surface area and increase convection. Some argue barrel fluting increases cooling because of the increased surface area.

Also carbon fiber isn't necessarily stronger than steel across the board, only in specific applications and specifications (which widely vary with CF). Spider silk is stronger than steel in right applications. While carbon fiber can be made stronger in some aspect (strong as defined by...tensile strength? modulus of elasticity? etc) by weight, how much volume does a pound of carbon fiber take up compared to a pound of steel? Steel is much denser and might win out in some applications while carbon fiber is more suitable in others.

I know one issue I've heard of with machining flutes into a heavy barrel is that the mill work might change the size of the bore slightly. That's why they cut the flutes, then bore/ream so I've heard.

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Tool deflection and any unrelieved/residual internal stresses on the material can lead to dimensional variations that don't appear "on paper". Metals also vary in composition from lot-to-lot. In aerospace, all the material dealt with is certified at every step starting from steel mills with a chemical analysis of the exact composition of a sample. Yet two identical steel alloys can vary one month to the next as far as how they react to machining tools, even if the analysis shows identical figures of impurities and alloying content due to so many other variables and factors. Every lot of material differs a little. Every heat treat differs a little. Nothing is 100% repeatable.

Carbon fiber dissipates heat amazingly fast. I used to heat up my HMR barrels fairly fast until I put a VQ barrel on, it takes a LOT to get it warm.

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To me that would mean that it is a good insulator and not a good conductor.

CF does not dissipate heat. Many motorcycle exhausts (muffler portion) are now made of CF. It's lighter, and it Keeps the heat in the exhaust which improves flow. The muffler doesn't get that hot, compared to aluminum, because it doesn't absorb and dissipate heat. This is why they are not using cf for engine parts. The internal temp rises dramatically causing parts failure. CF feels cool because it doesn't absorb the heat. I've been dealing with cf for many years now and it is great stuff. It is light and can be strong structurally if designed correctly. But it simply does not absorb and dissipate heat. I will say that I have no idea whether or not it will make your barrel wear out quicker because I don't have experience with that. But I do have experience with heat related issues and cf. It doesn't feel cool because it dissipates heat better. It feels cool because it doesn't absorb the heat to begin with.