To flute or not to flute? That is the question.


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KBintheSLC
November 5, 2007, 05:09 PM
I'm going to pick up a DPMS LR-308 soon, and I am wondering if I should get it with the fluted barrel instead of a standard bull barrel.

What are the real differences between fluted and not?.. (better heat dispersion, less weight, etc.)?

Never had a fluted barrel so your wisdom is greatly appreciated.

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ALS
November 5, 2007, 05:23 PM
A non fluted barrel has more accuracy so I'm told by military snipers.
Now the disclaimer, most of us on the board will never be good enough shots to see the difference between fluted and non-fluted.
I have two tactical's with fluted barrels. I got the fluted barrels on them for the LOOK. I know I'll never be good enough to shoot either gun to the pinnacle of their inherent accuracy. So it doesn't matter whether they are fluted or not.

JesseL
November 5, 2007, 05:25 PM
For a given barrel diameter, an unfluted barrel will be stiffer and heavier.

For a given barrel weight, a fluted barrel will be stiffer (and of a slightly larger diameter than an unfluted barrel of the same weight, but there' not much reason to care about that).

It sounds like you need to decide between a little more accuracy and a little less weight.

IMHO, issues of heat in relation to barrel fluting are a red herring. I doubt there is a significant difference and any gain in surface area is probably offset by a loss in heat sink mass.

mljdeckard
November 5, 2007, 05:27 PM
I've shot Remington 700 rifles with both, if there's a difference, I've never been good enough to draw it out. I'm thinking there are many other setup factors much more significant.

rjohnson4405
November 5, 2007, 05:49 PM
I sure like the way fluting looks, especially on a stainless barrel. :cool: As far as inherent accuracy the others have covered it.

KBintheSLC
November 5, 2007, 06:51 PM
I think the weight factor would sway me to go fluted. Like you guys said, the accuracy difference is not likely to be noticed.

Walkalong
November 5, 2007, 09:00 PM
IMHO, issues of heat in relation to barrel fluting are a red herring. I doubt there is a significant difference and any gain in surface area is probably offset by a loss in heat sink mass.
Fluting gains a significant amount of surface area, but If they flute only a small portion of the barrel, then it is not very worthwhile.

Most benchrest barrels are unfluted. If they were considered more accurate evryone would be using them.

They do look cool, save weight, stiffen the barrel, and give more surface area to help cooling. :)

RecoilRob
November 5, 2007, 09:07 PM
When I was shopping for my Bushy Varminter, I handled both stainless unfluted (Varmint Special) and the fluted Varminter. Shouldering both made me choose the fluted barrel. The unfluted was heavier than I felt comfortable with.

I don't think most people are going to notice a whole lot of difference in the performance of two rifles, fluted vs non-fluted. But, pick them up and you WILL notice a difference. Let that help you decide.

moojpg2
November 5, 2007, 09:34 PM
http://www.varmintal.com/aflut.htm good info on fluted barrels, seems to make sense to me.

Hypnogator
November 5, 2007, 09:55 PM
Really good info, moojpg2. From your page:

If fluting is done without introducing large residual stresses in the barrel it should improve accuracy by as much as 20% over a solid barrel of the same contour.

I'm getting a stainless Wilson barrel on my M4gery, and have been planning to have it fluted. I must confess, more for the looks than the accuracy, but it's comforting to know that it may actually improve accuracy.

RecoilRob
November 5, 2007, 10:14 PM
That quote is incorrect. It should read that the fluting would increase accuracy 20% over a barrel of the same 'weight'...not contour. Taking material from a barrel ALWAYS reduces its' stiffness and hurts the potential accuracy. If you read and grasp the entire article, you will see that the quoted statement is in error.

The beauty of fluting is the stiffer barrel...due to the increased diameter...vs a non-fluted barrel of the same weight.

USSR
November 5, 2007, 10:22 PM
I have several rifles with fluted barrels that I use in 1,000 yard competition, and here is my take on this. A fluted barrel is neither more accurate nor less accurate than a nonfluted barrel; that is more a function of the smith who does the chambering. Forget about fluting a barrel for heat dispersion purposes; the difference is negligible. I also would not flute a barrel strickly for the purpose of reducing a rifle's overall weight; there a easier ways to do that. IMHO, the only logical reason to flute a barrel is to allow you to use a long, heavy contour barrel and not have an unbalanced, muzzle heavy rifle.

Don

GunTech
November 5, 2007, 11:42 PM
If weight is really an issue, get a composite barrael. Mostly I think fluting looks neat. I have been told by several makers that to properly flute a barrel, the fluting should be done after drilling but before reaming and rifling, otherwise you are just inducing stress. I looked at fluting my 27.5 inch straight taper Hart bbl to lose soem weight. I decided to lose a few inches instead.

ROMAK IV
November 6, 2007, 12:24 AM
My Savage 112VSS has a fluted barrel, but the flutes are so small they are probably more decoration than anything. As for your decision, I would suggest trying to find an example of each model and seeing which one seemed easier and more comfortable to shoot, From what I have heard from the various DPMS owners, even the thinner 16" barreled rifles are exceptionally accurate. Heavy barrels aren't necessarily more accurate, but they tend to be more consistant and the groupings don't shift when the barrel heats up.

S&WKING
November 6, 2007, 01:01 AM
i was in the same boat but didnt have much of a choice when i decided on DPMS 204 but if you do get the fluted get the black in the flutes it looks so nice but i have to wait 2 months to get mine

USSR
November 6, 2007, 08:54 AM
I have been told by several makers that to properly flute a barrel, the fluting should be done after drilling but before reaming and rifling, otherwise you are just inducing stress.

Yep. And the only way it can really be done without inducing stress or causing variations in bore diameter, is to be done on a barrel that is to be cut rifled. With button rifled barrels, contouring and fluting is done after the barrel is rifled.

Don

45crittergitter
November 12, 2007, 07:20 PM
RecoilRob is exactly right.

birdbustr
November 12, 2007, 09:29 PM
Looks like everyone has done some thinking about this fluting thing. I think really its just personal preferrence, but maybe there is some merit from the consensus. I personally have both of my big game rifles with fluted barrels mostly because of the cool factor.
1. Close to heavy barrel accuracy without the weight of heavy barrels.
2. Heat dissapation (sp?)
3. Stiffer barrel
4. They just look cool

Dan360
November 12, 2007, 09:55 PM
I have heard that some custom barrel makers refuse to flute their barrels due to risks and safety issues. I believe that Shilen goes as far as saying that fluting their barrel will void any warranty and that they don't recommend it at all on any barrel.

Richard.Howe
November 12, 2007, 10:15 PM
Fluting is a purely aesthetic decision, just like fluting a bolt, poking holes in your stock forearm, or jewelling your trigger face, period. The stiffness / heat dissipation talk is just that: talk. Yes, there are miniscule engineering differences. Do they matter? Nope. Not unless you plan on cutting your flute depth too close to the bore inside diameter. Then they matter a lot. :evil:

But I'll be the first to admit fluting -- especially spiral fluting -- looks really cool!

Rich

USSR
November 12, 2007, 10:24 PM
I have heard that some custom barrel makers refuse to flute their barrels due to risks and safety issues. I believe that Shilen goes as far as saying that fluting their barrel will void any warranty and that they don't recommend it at all on any barrel.

Ah, and what method of rifling does Shilen use? Button rifling. It's no wonder they don't recommend the procedure. As Boots Obermeyer said, "Any fool can pull a button through a barrel!"

Don

browningguy
November 12, 2007, 11:55 PM
RecoilRob, what the author said was :

Fluting the baseline barrel showed a reduction in group size of about 21%. Keeping the same weight and fluting the barrel with a 1.222" muzzle diameter reduced the group size by 23%

So he believes that group size can be improved by fluting over the same contour unfluted barrel, and an additional improvement by using the same overall weight fluted barrel.

I happen to agree with most others that fluting will probably not improve accuracy in most barrels to to manufacturing stresses. Even though I am not an FEA expert, I wonder why you couldn't engineer a fluted tube to be stiffer than the original structure, it seems imminently doable to me.

USSR
November 13, 2007, 08:52 AM
Quote:
Fluting the baseline barrel showed a reduction in group size of about 21%. Keeping the same weight and fluting the barrel with a 1.222" muzzle diameter reduced the group size by 23%

So he believes that group size can be improved by fluting over the same contour unfluted barrel, and an additional improvement by using the same overall weight fluted barrel.

I happen to agree with most others that fluting will probably not improve accuracy in most barrels to to manufacturing stresses. Even though I am not an FEA expert, I wonder why you couldn't engineer a fluted tube to be stiffer than the original structure, it seems imminently doable to me.


First, the reduction in group size quoted above only reflects the results regarding THAT PARTICULAR BARREL WITH THE MACHINING WORK DONE ON THAT PARTICULAR BARREL. You simply cannot make an across the board statement that fluting (or nonfluting) will result in either a gain or loss in accuracy. The metallurgy of no two barrels is identical, nor is the quality of the machining the same.
Second, it is simply not possible to remove material from a barrel and have it be as stiff as the barrel you started with. The stiffness comparison is always made between two barrels of an identical length and weight.

Don

Joe Demko
November 13, 2007, 10:17 AM
I have a fluted Bushmaster carbine. It handles better than the same carbine did with a non-fluted full diameter barrel. It's also damned accurated, but that isn't a function of the fluting.

Mute
November 13, 2007, 01:35 PM
It's simple physics. You flute the barrel, it will not be as stiff as it was before the fluting. Period.

tjj
November 13, 2007, 08:11 PM
Some of you machinist types out there may know this.

Do you know what happens when you machine a groove into a steel rod or bar?

Well???? I don't know either. That's the problem. It will deform in an unpredictable manner due to relieving internal stresses in the stock material.

It's a mystery to me that fluted barrels shoot as well as some do. If flutes are shallow then there would be less tendency for deflection but I certainly can't guess what that amount would be. I'm not a big fan of fluted barrels.

RecoilRob
November 13, 2007, 08:15 PM
Varmint Al made a nice try at explaining things but he got some of his wording wrong. One place he says that fluting doesn't have any positive effect on accuracy, then he makes the conclusion you quoted.

Look at the chart below taken from his article. The bottom blue-dashed line is the baseline barrel. It is as heavy as the heaviest fluted barrel. The top RED line in the dynamic graph is the baseline barrel after fluting. Notice that it also has the HIGHEST muzzle deflection.

The 1.222 muzzle dia. fluted barrel weighs the same as the .8 dia. baseline barrel. The brown line represents its' deflection and it is the stiffest on the graph. This is what should be as the diameter is the greatest. If the 1.222 barrel was left UNFLUTED, it would be much stiffer yet and would be the stiffest one on the graph.

As to whether any of the simulated barrels would be more or less accurate than one of the others, it is far more dependant on the quality of the rifling, bore and barrel steel than if it is fluted or not or is lighter or heavier. Just because one rifle has a heavier barrel does not guarantee that it will outshoot the lighter one. Too many variables to predict that outcome by weight alone, but it IS guaranteed that the heavier contour WILL be stiffer....for what it is worth.

Varmint Al tried his best, but worded some of his conclusions contrary to what his graphs depict. Look at the one below closely and you will see that what he said in your quote is NOT what the graph shows.

browningguy
November 14, 2007, 12:11 AM
Thanks recoilrob, I actually set down with two of my FEA specialists today and they explained the whole theory to me. As you previously stated, you want max OD, they even brought up a tubeing string they are analysing and showed me how changes in the od affected stiffness.

I feel much smarter now, but I did get a headache from all the math.

quicktime
November 14, 2007, 08:49 AM
From what I have always been told you flute a barrel for weight considerations first then the increase in surface area helps cooling ( by how much is for the engineers to compute) and third for aestetic value. But it must be done prior to final machine work and heat treating.

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