Does anyone know how much weight reduction fluting gives?

It would depend on the number of flutes, some have 6 and some have 8, and the width, length and depth of the flute as that also varies from gun to gun. On average though, I would have to venture about 6-8 ounces. Not a lot but every ounce counts when building a light weight gun. The flutes also help to cool the bbl. and make it stiffer as well.

I understand there are variables. I am not planning a light weight but want a heavier weight barrel for the stiffness and heat dissapation for when at the range and figured if I have it fluted I could shed some weight for when hunting. I was thinking a standard varmint weight and then flute it.

I had a Shilen #2 fluted and it took off about 4 ounces. Would have to look it up to see what the exact weight savings was. I had him take off every shred of metal he was comfortable removing while keeping the barrel safe.

unfortuantely, the comments about fluting making the barrel stiffer and increasing the rate of cooling are both incorrect. Those 2 things get reapeated ad nausem in gun rags and then they get repeated by readers. I could go off on a tanget about how little gun writers actually know about physics, heat tranfer, thermodynamics, and basically everything else they try to sound like an expert in.

Removing metal from a barrel will always make it more limber. What is gained is when you compare barrels of equal weight. A lighter countour unfluted barrel is less rigid than an equal weight barrel that started as a larger diameter tube and was then fluted to bring it down to the weight of the first barrel. But the larger barrel was more rigid before the fluting and lost rigidity when the flutes were added.

If you are going to get any heat transfer benfit from increasing surface area, the barrel would have to be so hot to be able to measure the difference that the barrel would have to be so hot it was total toast and unuseable. But the point would be moot anyway, as the shooter would have sustained serious burns and the stock would be burned up. In a situation of forced convection, the heat transfer rate would be increased to a lesser extent, but you would have to be shooting inside of a tornado or hurricane.

ANy engineering student who has had the first couple of thermodynamics and strength of materials classes can see this, but the gun writers just keep repeating what the manufacturers put in their advertising when a new product comes out. It is not the reader's fault, and I have very big problem with how gun magazines operate. It seems to have gotten much worse in the past 10-15 years. They do not test things for themselves, instead oeferring to just repeat the manufacturer's "mantra of the month." Don't even get me started on short mags!

OK, better stop my rant now. There are 2 reasons to flute a barrel. 1. weight reduction. 2. you like the way it looks.

With weight reduction, you are usually better off going to the next smaller barrel contour. And real or theoretical loss of stiffness is hard to actually quantify in the field.

here's another thread on the subject.

quote:

Originally posted by Marc_Stokeld:
There are 2 reasons to flute a barrel. 1. weight reduction. 2. you like the way it looks.

Took the words out of my mouth. With #2 being the PRIMARY reason. I had my 30.06 bbl fluted for looks only. I couldn't tell you if it lost weight at all. It obviously did, but I can't "feel it."

The only other thing I'd add is that some smiths or bbl makers will tell you that fluting a bbl might hurt or change any current shooting loads you may have. I found that post fluting did not change a thing. The rifle still shoots 168 TSX bullets at .4" groups.

Thanks guys, looks like I would be better off just going the next barrel size down.

quote:

If you are going to get any heat transfer benfit from increasing surface area, the barrel would have to be so hot to be able to measure the difference that the barrel would have to be so hot it was total toast and unuseable. But the point would be moot anyway, as the shooter would have sustained serious burns and the stock would be burned up. In a situation of forced convection, the heat transfer rate would be increased to a lesser extent, but you would have to be shooting inside of a tornado or hurricane.

ANy engineering student who has had the first couple of thermodynamics and strength of materials classes can see this,

Then why - just taking the first example that comes to my mind - does the block of the Briggs and Stratton engine on my rotary lawn mower have flutes, or fins, or whatever you want to call them all around it? It doesn't get red hot, it sure isn't getting much forced air flow around it from the spreed I push the mower at, and I can't imagine that B & S make the blocks like that just for appearance.

it has to do with total surface area, geoemtry of the fins, and heat transfer coefficient of the materials. Apples to oranges. Would take a lot of very long and boring formulae and several semesters of hard work to adequately give a very detailed explanation.

Next time you see a Briggs and Stratton engine in a target rich praire dog town and set up as a high volume live vermint rig shooting .224 bullets at over 3800 fps, call me. I will fly out there and buy you a cold one. I will even buy you a steak that evening. Until then, the fluting makes no meanigful difference in the cooling of a sporter barrel.

"it has to do with total surface area, geoemtry of the fins, and heat transfer coefficient of the materials"

Marc,

You are correct except it is the thermal conductivity of the material which is why fins are typically aluminum to increase the heat transfer through the fin.

I do agree that fluting would actually increase the heat transfer due to the increased surrface area but the increase in surface area as far as increasing the radiative and convective heat transfer would be pretty much insignificant.

quote:

Originally posted by Marc_Stokeld:
What is gained is when you compare barrels of equal weight. A lighter countour unfluted barrel is less rigid than an equal weight barrel that started as a larger diameter tube and was then fluted to bring it down to the weight of the first barrel. But the larger barrel was more rigid before the fluting and lost rigidity when the flutes were added.

If you are going to get any heat transfer benfit from increasing surface area, the barrel would have to be so hot to be able to measure the difference that the barrel would have to be so hot it was total toast and unuseable.

Marc,
On the limber vs weight, I totally agree, and feel that is as well said as possible. On the surface area, you are correct as well, that the difference is small, especially when laid up against a real heatsink.


Redrover, Your mower engine is designed with fins to multiply (geometric increase) the surface area of the motor, to be heat sinks. These are THIN, and TALL in relationship to the thickness, meaning that they have a huge surface area, as compared to either potential condition the motor could have. Those being
1: a chunk of metal as large as the outer edges of the fins (heatsinks)
2: a chunk of metal with the minimum dimensions of the weight of the motor, without heatsinks.

Both conditions prove marc's post on the matter.

The issue with fluted barrels increasing the surface area of a barrel is without a doubt mathmatically accurate, but the EFFECT is algebratic... we'll assume, for the sake of time, it increases the surface area of the barrel by 1/3.

In terms of heatsinks, this is nil, and fairly immaterial...

take a look at your engine again, for a second, if you don't mind.

if you took and ground all the heatsinks (fins) off to the point there the surface area was 1/3 larger than the size of the block of the weight of the material, your would have "Wrinkles" rather than fins, and your motor would overheat in minutes....


overall, I think flutes look cool, on someone else's rifle

jeffe

Will-

that is what I was talking about when I wrote "heat trasnfer coeeficient of the materials." I am a little rusty on all of my heat transfer/thermo/fluids terminology-and have no intention of going through that hell again if possible!!! Man, talk about busting my balls for several quarters in a row.

But I always believed in the idea of a "well rounded student." My philosophy, as I would dierctly tell all of my professoers was "A well-rounded student begins with a well rounded transcript, so I need some of all the grades on there. And being an enginner, I lived and die by the bell curve in my data-a few A's, a few F's and a buch of C's in the middle!"

If you want to get really technical and look at theory and what is really happening but is too small to actually measure in the field is the color of the metal. If you could get the barrel to approach a black body as closely as possible, you could increas the rate of cooling. But even in a prarie dog metropolis, it wouldn't that would show up on an IR gun. The difference would be so small that the cost of coating a stainless barrel would never offset any savings in useable round counts down the bore. But on papaer it is there. Just wait till a gun writer hears that, does not fully understand it, and takes it out of context and starts that rumor going by most writers in every gun rag!!!

I believe that if fluting barrels had any real measurable effect on either weight reduction or heat dissipation you would see the military quickly and universally adopting the practice for infantry weapons, especially light and medium MG’s.

If a you like the look of fluted barrels or bolts then go for it, but don’t kid yourself about the other claims.

Dan Lilja has a spreadsheet on his website, which will allow you to play with fluting parameters (as well as contour, length etc.) for barrel weight calculations.


I believe you can download the spreadsheet via this page:

http://www.riflebarrels.com/products/software.htm

- mike

his relatively new "Number 0" contour is about th elightest you can get. COnsiderably lighter than any heavier contour that is fluted to the max. And they shoot well too as long as you let them cool.

With any light weight rifle, they usually shoot better than the shooter can wring out of them. Bench technique is so, so critical when dealing with true fly-weight rifles.