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Posted: 12/18/2003 1:44:23 PM EDT
What are the advantages, or disadvantes of a fluted barrel?  I am considering having the barrel, on the upper I am planning on purchasing, fluted to help reduce the weight, as well as for the looks.

Link Posted: 12/18/2003 2:37:42 PM EDT
Yes they are lighter, and are very strong. They also cool faster since there is more external surface area. Micro fluting will cool the fastest.
Good shootin, Jack
Link Posted: 12/18/2003 4:42:40 PM EDT

Fluting increases the "Koolness" factor.  The weight reduction can only be noted on a scale.  You probably won't "feel" the difference in weight when shooting or handling the gun.  

I have a rifle with a 24" Bull barrel.  It was heavy as hell!!  12 pounds with the scope, so I decided to flute the barrel ahead of and under the handguard.  The total weight went down a mere 6 ounces. Big deal!  But it looks nice.

I bead blasted the entire barrel after fluting then polished only the outside surfaces.  Gives an interesting visual effect.  Check it out....


Link Posted: 12/18/2003 6:51:22 PM EDT
Yeah same opinion here, I reccomend turning and fluting or just turning for weight reduction.  

I got a fluted 16in dissipator and it is pretty heavy. (the problem is the flutes don't run deeper in the part of the barrel that is .85in diameter than they do in the .75in diameter part.  the result is a barrel that no one will really call light.)

Link Posted: 12/18/2003 7:45:13 PM EDT
[Last Edit: 12/18/2003 7:46:55 PM EDT by Onslaught]
Weight is a relative thing...

My fluted Bushmaster 14.5" barrel FEELS lighter to me than a non-fluted one.  It feels about the same weight but different balance than my buddy's 16" RRA M4gery with the true M4 profile.  It feels HEAVIER than a 14.5" M4 barrel.

But I'm with Green0... I'm having my next one turned and fluted.

As for that "coolness" factor...  On the one hand, my rifle does look different than all those M4 clones at the range, but I don't like it.  I'm only having it fluted under the HG.  Just a personal thing.
Link Posted: 12/18/2003 8:04:18 PM EDT
[url=http://www.kurtskustomfirearms.citymax.com/releases/release/60917/68.htm] Here is a spec chart of barrel weights from KKF [/url]
Link Posted: 12/18/2003 9:24:28 PM EDT
I like the M4/M16A2 profile barrels better.  About the same accuracy, cheaper and less weight.  Especially for the 20".
Link Posted: 12/18/2003 11:36:49 PM EDT
I weighed my 20" HBAR upper with barrel that had been fluted. It weighed the exact same as a 16" HBAR. Around 8oz different.
Link Posted: 12/18/2003 11:49:42 PM EDT

Know any places that do micro-fluting?
Link Posted: 12/19/2003 11:15:23 AM EDT
Fluting will noticeably lighten the barrel but I was hoping to have a firm barrel that weighed as much as the less firm M4 barrel and that didn't happen (it's halfway there but halfway isn't all the way.)

The result is a rifle that I know mounting a KAC M4QD on will make the rifle too heavy so the choice is change barrels, or loose the bi-pod. and I like Bi-pods.
Link Posted: 12/19/2003 11:51:28 AM EDT
I have a 16" fluted barrel, from bushmaster and the flutes are pretty deep. It is noticably lighter than the HBAR. It is only slightly heavier (according to Kurt's chart) than an M4 barrel that is turned down. The fluted barrel will be more rigid than than M4(of the same wieght) and will handle the heat better.


That said, I also have a SLW barrel, because that's the only way to go if your going for just lightweight.

Link Posted: 12/21/2003 5:22:48 AM EDT
Thanks for the input, a fluted barrel will do very well for what I'm wanting.  Russ, the visual effect on your bull barrel is cool, looks great.  

Link Posted: 12/21/2003 5:24:41 AM EDT
I'm another fan of fluting.
Link Posted: 12/21/2003 5:19:50 PM EDT
Not a Llama

I can't recomend anyone off hand, but there are several out there. Call around to any of the barrel makers, Douglas comes to mind but not sure. A good gun smithing place can do it. The cost is greater for micro, but to me it is the best way to go and worth it.
Good shootin, Jack
Link Posted: 12/21/2003 5:43:18 PM EDT
[Last Edit: 12/21/2003 5:52:52 PM EDT by Boomholzer]
Any inset i.e. fluting will not give you any great additional rate in barrel cooling. Conductive and radiative modes of heat transfer with the normal amount of additional surface area give no substantial benefits.

If your willing to give up a certain amount of rigidity for weigh, it works. Any added benefit of cooling is poor.  The detrimental effect of poorly machined barrel flutes are of greater significance. Any error in length, width, and depth of the individual flutes will cause different expansion rates in the barrel. They already do as in post front site application where a relatively  large thermal mass suddenly meets a low thermal mass. However any barrel deviation should cancel out if they are machined equally.

Any added benefit of rigidity, strength or accuracy is pure hype.

If there is any application where is would be of benefit, it would be in a non-target semi-auto lightweight configuration. Fluting a >9lb bolt rifle with a heavy barrel is pure nonsense. My stance is if you want a lighter configuration get a smaller barrel profile.

They are not "very strong" in any application, you are sacrificing strength for weight. I give you that a fluted barrel is stronger PER WEIGHT (more or less given the axis) then   the same mass, which would determine a smaller O.D.  In the same time you are adding higher order barrel harmonics and an increased chance of a non-uniform machining.
If it were not for the high tech look, which manufactures play off of, the fad would have disappeared long ago.
Link Posted: 12/21/2003 6:10:47 PM EDT

Rock Island did extensive testing of various barrel cooling approaches. A micro fluted barrel came out the winner in cooling. The cost of doing micro fluting in an accurate manor is another story. However with the new CNC turning abilities combined with the 4th axis, the fluting is as accurate as a simple turned barrel. In fact if you compare wt. for wt. the fluted barrel is less prone to harmonic vibration changes do to it being more rigid pound for pound. Anything poorly executed isn't gooing to work as well as something properly done.
Good Shootin, Jack
Link Posted: 12/21/2003 7:00:09 PM EDT
What is the 4th axis?

Outside of the machining and such, I’ll tough on the additional axis of time.

The BOSS system uses gas pressure from the escaping bullet to present a sort of “impedance or resistive load to the barrel” basically, it acoustically (not in a vocal sense but in the given frequencies that a barrel conducts) loads the end of the barrel so that such vibrations (when the bullet moves down the barrel and normally during peak pressure for it is not a variable process) are terminated and not reflected back down the barrel to cause sum mixing of vibrations.

To more simplify, when the cartridge goes boom, the ongoing gas pressure energy is used to counteract vibrational energy to keep a barrel from vibrating at the main harmonic (fundamental vibration determined by the length and mass) as the bullet travels down the barrel.

Infinite rigidity of a barrel leaves this equation. Discontinuities in a barrel, such as fluting can either be null (only with an exact cartridge outside of normal load parameters) or detrimental.   Post front-site fluting presents a 2nd strong vibration reflection before the bullet even hits the gas port.  The new order vibrations, are present when the bullet never reaches this point and the accuracy detriment is dependant on the created discontinuity. These points are super anal but someone will add how a fluted barrel makes it all good.
While the effects are null in a observational point of getting a bullet to exit a barrel, yea! It looks cool.
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