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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
ABS carbon barrel heat dissipation......
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<blockquote data-quote="Buffalobob" data-source="post: 115410" data-attributes="member: 8"><p>A month or so ago, I took a little time and checked the thermal conductivity of barrel stainless steel versus carbon fibers. Conductivity is a measure of the speed at which heat will flow from one spot to another or from one area to another. It appears that there are so many differrent formulations of fibers that you can make it do whichever you want it to insulate or dissapate. Some types of fibers are a 100 times more conductive than barrel stainless steel and some are only two times more. Then there is the gel that is used to bind the fibers together and make it stick to the barrel (if any). I do not know what it is but it would have a major bearing on heat transfer. Even a thin film can be a major barrier or help to heat transfer. An example of this is in building tank armor. A thin layer of air will shut down a lot of heat transfer and will absorb a lot of shock transmission so air sandwiched between steel layers is better protection than solid steel for a shaped charge explosive head. So any thin film between the steel and the fibers is vitally important to know about.</p><p></p><p>My original impression on carbon fiber was the same as Kirby's that it was used as insulation and what I now believe is you really must look carefully at the metal of each application and the type of carbon fiber that is used in order to determine what the final outcome will be. Heat may be retained or transfered. A lot of science involved in order to get the right combination.</p><p></p><p>Just one note on the thermal imaging. The external surface of the barrel is obviuosly not what is at issue. It is just what can be measured. The critical area is the first few 0.01 inches of of steel inside the barrel. There will be a temperature gradient from the throat area inside the barrel to the outside. The current theory on fire cracking inside a gun barrel or even other steel seems to be linked to the inside (not outside) surface layer temperature versus the temperature just a few hundreds of an inch deeper in the steel and the coeffeicient of expansion of the steel. The difference in temperature in those few hundreds of an inch of steel casues differences in expansion and therefore stress cracks appear. The heat also causes some hardening of the steel which then not only increases the stress fractures but also creates a spalling effect. In other application besides barrels, the term heat cycles is used. In other words, a boiler is fired up and run at temperature (or a car engine) for a while and then shut down and is considered one cycle. With a bolt action rifle, it is unclear what a cycle is. I have seen demonstrations where M-60 (308) machine guns were fired until the rounds were cooking off from the chamber temperature and then continued until the barrel was actually red with heat. This one time destroys a barrel in one "cycle". The question of what actaully causes heat checking is still being debated and thusly the cure for it is still at question. And finally, I would simply say that my looking into it on the internet does not constitute any real research of a scientific nature. If you want to find bad science the internet is definitely the place to go. Lastly, this post is not to contradict anybody or anything it was just that I tried to spend some time understanding what was actaully going on and thought that I would post my understanding of carbon fiber barrels and throat life. Mostly I concluded that there is a big debate over what causes heat checking - except that it is heat.</p><p></p><p>If carbon wrapped barrel help throat life then it is going to be a big boon to people who shoot lots of rounds. </p><p></p><p>Editorial note:</p><p>It fits here a little better than over there.</p><p></p><p>--------------------</p></blockquote><p></p>
[QUOTE="Buffalobob, post: 115410, member: 8"] A month or so ago, I took a little time and checked the thermal conductivity of barrel stainless steel versus carbon fibers. Conductivity is a measure of the speed at which heat will flow from one spot to another or from one area to another. It appears that there are so many differrent formulations of fibers that you can make it do whichever you want it to insulate or dissapate. Some types of fibers are a 100 times more conductive than barrel stainless steel and some are only two times more. Then there is the gel that is used to bind the fibers together and make it stick to the barrel (if any). I do not know what it is but it would have a major bearing on heat transfer. Even a thin film can be a major barrier or help to heat transfer. An example of this is in building tank armor. A thin layer of air will shut down a lot of heat transfer and will absorb a lot of shock transmission so air sandwiched between steel layers is better protection than solid steel for a shaped charge explosive head. So any thin film between the steel and the fibers is vitally important to know about. My original impression on carbon fiber was the same as Kirby's that it was used as insulation and what I now believe is you really must look carefully at the metal of each application and the type of carbon fiber that is used in order to determine what the final outcome will be. Heat may be retained or transfered. A lot of science involved in order to get the right combination. Just one note on the thermal imaging. The external surface of the barrel is obviuosly not what is at issue. It is just what can be measured. The critical area is the first few 0.01 inches of of steel inside the barrel. There will be a temperature gradient from the throat area inside the barrel to the outside. The current theory on fire cracking inside a gun barrel or even other steel seems to be linked to the inside (not outside) surface layer temperature versus the temperature just a few hundreds of an inch deeper in the steel and the coeffeicient of expansion of the steel. The difference in temperature in those few hundreds of an inch of steel casues differences in expansion and therefore stress cracks appear. The heat also causes some hardening of the steel which then not only increases the stress fractures but also creates a spalling effect. In other application besides barrels, the term heat cycles is used. In other words, a boiler is fired up and run at temperature (or a car engine) for a while and then shut down and is considered one cycle. With a bolt action rifle, it is unclear what a cycle is. I have seen demonstrations where M-60 (308) machine guns were fired until the rounds were cooking off from the chamber temperature and then continued until the barrel was actually red with heat. This one time destroys a barrel in one "cycle". The question of what actaully causes heat checking is still being debated and thusly the cure for it is still at question. And finally, I would simply say that my looking into it on the internet does not constitute any real research of a scientific nature. If you want to find bad science the internet is definitely the place to go. Lastly, this post is not to contradict anybody or anything it was just that I tried to spend some time understanding what was actaully going on and thought that I would post my understanding of carbon fiber barrels and throat life. Mostly I concluded that there is a big debate over what causes heat checking - except that it is heat. If carbon wrapped barrel help throat life then it is going to be a big boon to people who shoot lots of rounds. Editorial note: It fits here a little better than over there. -------------------- [/QUOTE]
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