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Posted: 10/5/2004 10:09:08 AM EDT
| What`s the deal with having a Fluted AR-15 barrel? Does it weigh that much less or cool that much faster? Gimme the low down. Thanks |
It looks *really* cool, especially if it is spiral or diamond  Obviously there is some weight loss (a few ounces usually) , greater heat dissipation (although not enough to notice), and some loss in rigidity (although not enough to affect accuracy) , but can anyone really say that they have noticed a difference? I never have... I have always opted for fluting when given the choice -- simply because it looks good and I have yet to encounter any reasons not to. |
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Fluting can offer some advantages. First is cooling. It increases the surface area of the barrel. Therefore, it will radiate heat faster than a non-fluted barrel. You have to decide whether this is always an advantage as depending on your handguard, you could find your support hand getting hotter, faster. Weight & rigidity. First off, you need to look at two diameters, the outer diameter of the barrel, and the inner diameter at the bottom of the flutes. Usually, a fluted barrel will fall somewhere in between a skinny and an hbar in weight. It will be stiffer than a skinny barrel, has more mass and is therefore a better heat sink, and because of the fluting, will radiate heat faster and cool down faster. But, it will weigh more. Compared to the hbar, it won't be as stiff, but the difference probably won't be noticeable. It will weigh less, will heat up faster, but also cool down faster. If the barrel is properly stress relieved after the fluting, I would say it is probably a good thing. All of the foregoing is based upon a LOT of research and careful reading, not personal experience. Take it for what its worth. |
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The 'Heat Dissipation' issue is highly overrated. Practically there is no differnence on a rifle barrel (twice near nothing - is still near nothing) especially as you have handguards to help hold it in... Weight savings, there is some. With the 24-26" barrels you look to save 0.8lbs. With a 20" you save half a pound (its weight is halfway between an HBAR and a A2 profile). With a 16" you save 0.2lbs (almost a quarter of a pound). Hardly worth it IMHO, as the M4 profile will save you half a pound and the lightweight will save 0.8lbs off the weight of an HBAR. |
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I have all of my AR barrels fluted. On a 20", Bull barrel the "before and after" wall almost 1 lb. I consider that a HUGE savings. And as far as the heat dissipation, it's also HUGE. You guys are most likely not useing the same type rig I have but I have hunted prairie dogs for 25 years and 12 of them with an AR. Two huge factors on barrel heat are: Fluting, and Moly-coated bullets. I have hunted side-by-side with my Son, using the same ammo, on the same day, in the same dog town and I can shoot twice as many shoots per hour as he can without the fluting. I have observered about the same cooling/lack of cooling with the Moly bullets vs non-Moly. I've done the math on the fluting and on my 20", bull barrel I have over 105% more surface area than non fluted. How can you look at figures like that and think that cooling won't be increased? Have you ever looked at the back of a stereo and seen those nice looking heat sinks? They didn't make them shaped like that for weight reduction, they were looking at increasing surface area for cooling. |
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To address the stiffness question, I think I can sum up the answer like so: A fluted barrel of weight X, will be stiffer than a non-fluted barrel of weight X. So basically, if you take an Hbar and flute it, it will be less stiff than a non-fluted Hbar. But! If you get a barrel that's heavier than an Hbar, and the fluting removes weight so that it weighs the same as an Hbar, then the fluted one will be stiffer. |
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No, that's not the concept on barrel stiffness/fluting. If you take two identical barrels with the same contour, flute one of them (and I don't mean cosmetically flute them). Put each of them in a receiver, hang a given weight from the end of each of them, the fluted barrel will "bend" less than the non -fluted barrel. A round tube has less strength, from a bending force, than just about any other shape of the same mass. When you cut flutes into a barrel, you are changing the structural shape of the barrel. The 12 vertical walls that are formed from the 6 flutes act as an I beam would act while trying to bend it. The difference is that the barrel has 12 "I beams" every 60 degrees around it's circumference. This makes the barrel stiffer in more than just two planes. Trust me, the only "down side" to fluting is the cost of having it done. |
No Sir, with respect, that's not correct. It flies in the face of simple and unavoidable physics.
Now THAT is on the right track. In your own words, in two objects OF THE SAME MASS, a cylinder will be more flexible than a fluted or angled object. Although a solid rod will have LESS strength than a Hollow rod OF THE SAME MASS, but that's not applicable here since we all have a hole in our barrel.  An HBAR has MORE MASS than a FLUTED HBAR, and therefore would be STIFFER than the latter. BUT a FLUTED HBAR would be STIFFER than a MEDIUM CONTOUR barrel of the SAME MASS. Remember, when you flute a barrel, you are not only "changing the structural shape of the barrel", you are also REMOVING MASS. Having said all that, I'll add that I prefer fluted barrels over HBARs, and will probably continue to go that route when I want lighter weight, but still stiffer than an A2 profile. I don't like the looks of the flutes though, so I don't fall into the "coolness" factor range. While we're talking science, weight savings, and fluting... I gotta remind you guys of this fact too... When someone says "it's only a few ounces, how can that matter?" Well you gotta remember that a few ounces is a few ounces, BUT a few ounces placed on a FULCRUM that's got a full 24" of working leverage is a LOT of weight savings. In other words, a few ounces on the barrel end translates to several times that on the grip end. Less of course at the handguard point, but still more than a few ounces. Simple 8th grade science 
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No, I was only comparing the tube to other shapes of the same mass, rectangle, square, triangle. If you took the material that you removed during the fluting process and were able to put it on the outside diameter of the un-fluted surface, then that barrel would be A LOT stiffer than the tube of the same mass. I have had it demonstrated to me years before the industry was fluting barrels. If you don't agree with fluting,.......don't do it. I still maintain the only "down-side" to fluting is the cost. |
The physics doesn't support this. Given the same material and same diameter, a solid will be more rigid than a tube, fluted tube, or any other skeletonized shape. The solid will be heavier though. The reason i-beams are used is because of the huge weight reduction, not because they are stronger than solid beams of the same external dimensions. They are used because they have a better strength to weight ratio, are much easier to assemble, etc. A fluted barrel will be stiffer than a non-fluted barrel of equal length and weight, due to the larger cross-sectional diameter. |
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Weight Savings. Carbine: It is easier to stop a lighter barrel on the target without the added inertia the extra weight would cause. Precision Rifle: So you can pack the rifle farther and be able to use it when you get to your destination. MT (but I could be wrong) |
| I-Beams are stronger than a solid Beam...Don't think so? Take a long solid square beam that is 2 inches high, 2 inches wide...and 20 feet long...Then take an I-Beam of the same scale...hold one end of each beam down on a table so that the extra 16 feet or so is hanging off and see which end is hanging down more at the other end. OR...make a 3 foot long solid beam by sticking a bunch of cardboard strips together and then make an I-Beam out of the same cardboard....Lay the beams aross something to act as a bridge...Then apply weight to the center of each beam....See which one bends first...Won't be the I-Beam |
That has nothing to do with strength and everything to do with the additional weight of the solid vs. the I beam. It is mass vs. gravity. The real strenght test would be to stack additional weight equal to the difference between the two on top of the surface of the I-beam and then run comparisons. |
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Well.... Take a solid 20 foot long beam....It will bend so much....Then Cut material out of it to shape an I-Beam..It will bend less. Take a solid 20 foot long barrel....It will bend so much...Then cut material out of it (fluting)...it will bend less. When you flute a barrel you don't take that removed steel and stick it back on top of the barrel do you? Adding the difference in weight just negates the whole purpose. |
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