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Old July 30, 2020, 10:03 AM   #1
Bart B.
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Does Fluting a Barrel Make It Stiffer?

A popular benchrest rifle barrel maker says it depends on how it's measured:

https://bartleinbarrels.com/barrel-faq/

Mechanical engineers dealing with vibration analysis say fluting removes metal that resisted bending, compression and expansion so it's less stiff. Other barrel makers agree. .
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Old July 30, 2020, 10:51 AM   #2
Jim Watson
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I thought that one had been kicked around enough to not be controversial.

What I thought interesting was Bartlein's statement that a silencer will reduce barrel life.
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Old July 30, 2020, 11:19 AM   #3
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I never choose fluting unless it's for weight reduction for a hunting rifle. The rest of the reasons are mojo-voodoo beyond my pay grade. I do enjoy reading it though.
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Old July 30, 2020, 11:31 AM   #4
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I always thought it was a cooling thing,,,

I always thought it was a cooling thing,,,
At least I read that somewhere and thought it made sense.

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Old July 30, 2020, 11:42 AM   #5
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Quote:
Originally Posted by Jim Watson View Post
I thought that one had been kicked around enough to not be controversial.

What I thought interesting was Bartlein's statement that a silencer will reduce barrel life.
No doubt that suppressors shorten the life of a barrel even on bolt guns, how much it's hard to say. I've been using suppressors for about 6 years now on both rimfires and centerfires. The rimfires are of the most concern, if the suppressor isn't cleaned often lots of carbon falls down the barrel when it's picked up and held vertical to the point the action is full of it and even a bolt gun won't function, it has to increase barrel wear.
I take them off often and tap them on a hard surface to see how much carbon comes out, if it's very much I use a clean one{I have three rimfire suppressors} and put it in a can of solvent for cleaning later.
Centerfire suppressors don't seem to get very dirty, I blow them out occasionally with a air compressor.
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Old July 30, 2020, 12:43 PM   #6
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Quote:
Originally Posted by Bartlein Barrels
Does fluting make the barrel stiffer?
If you we’re to put a weight in the center of the barrel or hang it on the muzzle end it will flex more than a barrel without flutes with the same contour.
So he is saying, no, it does not.

The way I understand it, a fluted barrel will be less stiff than an un-fluted barrel of the same profile, which is what Bartlein is saying above.

I have heard that a a fluted barrel will be more stiff than an un-fluted barrel of the same weight, but I have never seen that actually tested. Then again I haven't looked, but it seems logical, for the same weight the fluted would have a larger profile.
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Old July 30, 2020, 12:53 PM   #7
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Yes, barrels will cool a little bit faster with more surface area, maybe 5%.

A properly stress relieved and installed non-fluted barrel will shoot to point of aim for several dozen shots fired several times per minute. One test with a 308 Winchester put 40 shots inside 2 inches at 600 yards
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Old July 30, 2020, 12:54 PM   #8
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Fluted barrels look cool especially if it's done in a spiral, I'm sure there are exceptions but I've never seen one that was really accurate-under 1/2 moa.
I've had one, a E.R. Shaw 358 winchester, the gun was way more accurate than needed for a big game rifle with many loads sub moa, I wouldn't buy varmint or br rifle with fluting though.
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Old July 30, 2020, 01:31 PM   #9
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I've read theories that since a fluted barrel has more surface area it is less likely to flex. I know that corrugated sheet metal is much less likely to bend for that same reason. A steel I beam, or even L shaped metal bar stock is far less likely to bend than a solid piece of metal rod of the same diameter. But I've never seen any definitive proof that the same principle applies to rifle barrels.

Until I see proof I'm going to say that a fluted barrel is no more, or less accurate (or stiff) than an unfluted barrel of the same diameter. But I'm willing to keep an open mind. But show me the proof 1st.

There are 3 ways for a hunter/shooter to make his rifle lighter. You can shorten the barrel, which will also make it stiffer but at some velocity loss. You can make it thinner, or you can keep the same overall diameter and flute it.

In my experience a fluted sporter weight barrel can be close to the same weight as a thin mountain rifle barrel contour and be just as accurate as a heavier sporter weight barrel. And I don't lose the velocity of the shorter barrel. If I'm looking to reduce the weight I'm carrying I believe fluting is the better option.

I'm sure fluting also allows a barrel to cool faster. But for me that isn't an issue.
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Old July 30, 2020, 02:06 PM   #10
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It is my belief that it is about cooling. As stated above more surface area allows the barrel to cool quicker. I guess we could google it but what fun would that be.
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Old July 30, 2020, 02:19 PM   #11
Bart B.
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The most simple reasoning that fluting a barrel makes it less stiff is material was removed that resisted bending. Surely, this is not too hard to understand.

https://web.archive.org/web/20141024...relFluting.asp
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Old July 30, 2020, 02:33 PM   #12
Double K
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Most of the fluting is done after the barrel is drilled and rifled, machining afterwards might effect barrel stresses hard to say but I've never seen a br gun that was fluted.
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Old July 30, 2020, 03:09 PM   #13
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thank you bart b. +1
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Old July 30, 2020, 03:32 PM   #14
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Quote:
Originally Posted by Bart B.
The most simple reasoning that fluting a barrel makes it less stiff is material was removed that resisted bending. Surely, this is not too hard to understand.

https://web.archive.org/web/20141024...relFluting.asp
So someone did test it.

Quote:
Originally Posted by SniperCountry test
Results

12 BVSS Fluted (OD 0.850") versus 10 FP Plain (OD 0.850")
Weight: 38% less
Stiffness (as a function of Moment of Inertia): 43% less

The fluted barrel is much lighter, much less rigid, but has much more surface area than a solid barrel with the same overall outside diameter.

12 BVSS Fluted (OD 0.850") versus Light Varmint (OD 0.700")
Weight: Same
Stiffness (as a function of Area of Moment Inertia): 25% more

The fluted barrel is much more rigid, and has much more surface area than a solid barrel of the same weight.
A fluted barrel is less stiff than an un-fluted barrel of the same profile/diameter.
A fluted barrel will be more stiff than an un-fluted barrel of the same weight.
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Old July 30, 2020, 03:34 PM   #15
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I have a Savage .308 replacement barrel that I had fluted when I ordered it.
It has averaged 0.438 for 167 5-round groups.

I also have a Savage .308 10 FCP-K that came formthe factory with a fluted barrel.
It has averaged 0.442 for 252 5-round groups.

Both barrels out shoot the original Savage barrel that was un-fluted.
I can't confirm that fluting makes barrels less accurate.
But my data says they can be at least as accurate and perhaps more accurate.

As for rigidity - while it might seem that losing mass in the steel would make the barrel more flexible, it isn't necessarily just the mass of material that makes steel more rigid.
Ever notice that bead rolling to put ridges into steel panels makes the panels more rigid. No added mass, only changes in the surface adds rigidity. Fluting changes the surface, but I'm not sure that the changes would be conducive to adding rigidity.

I don't claim that fluted barrels are more rigid than non-fluted barrels, but I guess my data confirms that they can be as accurate.
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Old July 30, 2020, 04:02 PM   #16
Bart B.
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I've seen fluted barrels in all sorts of match winning rifles.

Last edited by Bart B.; July 30, 2020 at 04:12 PM.
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Old July 30, 2020, 04:21 PM   #17
Bart B.
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Quote:
Originally Posted by Rimfire5 View Post
Ever notice that bead rolling to put ridges into steel panels makes the panels more rigid. No added mass, only changes in the surface adds rigidity.
Yes, but its length or width is less. And it's thicker so there's more metal in the vertical plane. But its weight stays the same.

Barrels weigh less after fluting. You could affix the strips of metal that were in the grooves on top of the ribs so the barrel weighs the same and be stiffer.

Last edited by Bart B.; July 30, 2020 at 04:49 PM.
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Old July 30, 2020, 05:27 PM   #18
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Your question isolates stiffness as a criteria.
That can be checked . Any number of setups will accomplish the same thing,
Use a repeatable load (a weight) and a dial indicator to measure deflection.
That will measure stiffness.
As far as heat..depends on what you are doing. If you are shooting slowly and waiting for a particular temp,the additional surface area may help.
But a small team trying to disengage with massive fire ,one full auto mag dump after another, will find the barrel mass of a non fluted H-Bar will soak more heat than a fluted bbl. Its a mass thing.

Accuracy? I'm sure there are examples of finished barrels that were then fluted that shoot very well.,and smiths who will say "I've been fluting barrels for 20 years and they dah....dah...dah.... OK. I'm not there.

I can be skeptical.

IMO,the fluting should take place early in the barrel making process,and stress relieving ,then rifling and lapping. I'll leave that to the barrel makers to define,Its probably different for cut rifled vs button rifled.

No machining cutter is perfectly sharp. They may largely cut chips,but to some degree,steel gets beaten and displaced, The effects may be infinitesimally small, but I would guess fluting a barrel would make the bore grow in dia,be less round,less straight,and rubber band like stresses would be introduced.

That they still shoot may be largely about the unfluted section at the muzzle that says "goodbye" to the bullet.

I have nothing against fluting. I agree weight for weight,a fat fluted barrel will be more rigid than a skinny unfluted barrel.

But,IMO,fluting should not be an afterthought add on. I want it designed into the barrel making process by the barrel maker.

Something I know nothing about: How the barrel is "tuned" in harmonics,where it will flex,where it is rigid,where to place mass, all figures into the accuracy.
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Old July 30, 2020, 05:53 PM   #19
Bart B.
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Quote:
Originally Posted by HiBC View Post
IMO,the fluting should take place early in the barrel making process,and stress relieving ,then rifling and lapping. I'll leave that to the barrel makers to define,Its probably different for cut rifled vs button rifled.
Air gauging barrels for groove diameters before and after fluting has shown....

Button rifled ones get smaller.

Cut rifled ones change very little, if at all.

Hammer forged barrels get larger.

All only under the fluted area.

Last edited by Bart B.; July 30, 2020 at 05:58 PM.
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Old July 31, 2020, 06:07 AM   #20
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Does anyone think Bartlein going to sell fluted barrel that going to be less accurate then non fluted barrel.

https://bartleinbarrels.com/payment/

I have Bartlein 5r fluted barrel on 30-06 and Rock Creek 5r fluted barrel chamber for 270Wby.

I'm more concern on who's going to chamber vs worrying about fluted barrel.


When I was shooting BR, I purchase Skip Otto 6ppc that he won Super Shoot with. I got brass, dies and 5 barrel that he fluted.

https://www.practicalmachinist.com/v...luting-253498/ go down to post #14
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Old July 31, 2020, 07:36 AM   #21
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Just to toss a little gasoline on the discussion (and perhaps bait unclenick into the discussion since I highly value his wisdom), I have noticed when attaching a pressure trace to my rifle's barrels the characteristics of the trace vary significantly depending on where I put the gage--it appears that all other things being equal the thicker and more consistent (meaning distance from ID to OD is uniform) the metal is, the more consistent the modulus elasticity is. The molecular quality of the steel itself probably plays a big role. But this may be just fizzics speculation (or misunderstanding) on my part.
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Last edited by stagpanther; July 31, 2020 at 07:43 AM.
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Old July 31, 2020, 08:42 AM   #22
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I don't care either way, if I order a fluted barrel it is trying to save some weight. Like the last barrel I ordered an 18" magnum contour Savage prefit, I had it fluted to try and make an overall weight goal of the rifle. I missed it by at least a pound over my goal weight, but I needed a heavier contour barrel to have enough muzzle diameter to thread for my suppressor.



I was hoping it would come in at 2.5 lbs, not 2 lbs 15 ounces (14.9oz). Easiest way to save weight when building a rifle is barrel and stock, I missed on both accounts because I didn't want to spend the money for a carbon fiber stock or custom contoured or carbon fiber barrel. To save that pound of weight would have cost me about $62.50 an ounce.

I look at it as a learning experience, and I'll shoot it and build a true custom if it works as well as I hope. I'll try to go from an 11 pound scoped rifle down to an 8 lb scoped rifle. That would sure make it more enjoyable to carry.
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Old July 31, 2020, 10:04 AM   #23
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Looks cool--like a narwhale tusk.
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Old July 31, 2020, 10:25 AM   #24
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Engineering is great.
Till the first turn.

Paper & real world experience end up being very different things.
Reduced weight be darned, people keep forgetting that when it comes to metals, form has it's own structural function.
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Old July 31, 2020, 10:36 AM   #25
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If your sundeck is made with 2 x 6 boards vertical set against each other, will it be stiffer if every other one is replaced with a 2 x 4?
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