Fluted Bull Vs Smaller Barrel?

A

AdamZx3

Guest
I was wondering why exactly a fluted barrel is better than a barrel with a more narrow taper that has the same surface area as the fluted one?

If they had the exact same surface area, wouldn't they both weigh the same? I suppose the fluted might have more stiffness than the smaller barrel?

But also wouldn't the fluted barrel be less stiff with the extra material removed?

The rifle would have a goal to be lightweight, fired about 5 times rapidly max, and have a short 20" barrel (so stiffness might not be an issue?) It would also be chambered in 308.

Several searches seem to be debatable at best, any opinions?
 
I'm not understanding what you are asking. If a sporter tapered barrel has the exact same surface area of a fluted barrel then it is going to be quite a bit heavier. If you are shooting 5 shots, the surface area is not doing you a bit of good. Mass is doing you the good. If you are trying to cool that barrel to shoot more, then flutes could possibly help-some.

I can't believe how many people are under the impression that if you take a given barrel and then flute it, it becomes stiffer!! It may cool faster and look cooler but it will be less stiff if any different. I have even seen adds that state that you can increase the stiffness of your barrel by fluting it???
 
Yeah, Dennis, I've heard the same kind of crap.

Adam--
A fluted barrel is stiffer than a solid barrel of the same weight.
A fluted barrel is lighter than a solid barrel of the same diameter.

The whole cooling thing is sort of secondary.
 
A fluted barrel will be lighter than a solid one for the same section modulus.
 
papapaul said:
A fluted barrel will be lighter than a solid one for the same section modulus.
Click to expand...

....which, according to Wikipedia, means:

"In structural engineering, the section modulus of a beam is the ratio of a cross section's second moment of area to its greatest distance from the neutral axis.

The section modulus is directly related to the strength of a corresponding beam. It is expressed in units of volume, e.g., mm<cubed>."


I guess that says it all.
 
Thanks Guys, That helps :)

I thought that surface area might not be the best description! Mass, weight, or modulus would be much better descriptive words :)

I also thought that the extra stiffness from the flutes was hype.....I cant see how removing material can make something stiffer.

Just so I understand correctly , having flutes in a larger barrel doesn't have any accuracy advantages over having a smaller barrel of the same mass/modulus ?
 
Last edited by a moderator:
AdamZx3 said:
Thanks Guys, That helps :)

Just so I understand correctly , having flutes in a larger barrel doesn't have any accuracy advantages over having a smaller barrel of the same mass/modulus ?
Click to expand...

Mr. AdamZx3, true as long as you understand correctly and the larger fluted barrel stiffness doesn't count for anything.
The larger fluted barrel will be stiffer than the smaller barrel of the same mass.

Con
 
Let's get practical for a moment. The only time you can directly compare a fluted and an unfluted barrel of the same weight and length for stiffness is when they are cylindrical, and you have no contour rules.

Once you introduce a barrel taper, it gets very tricky. Specifically, what are you going to do with the weight savings with the fluted barrel? In benchrest, with the 5-inch straight allowed in front of the breech, you could increase how long a straight portion you have with a fluted barrel while still making the weight limit. The longer 1.250 cylindrical portion will increase stiffness. (Check the Lilja site).

On the other hand, you could keep the longer cylindrical section with an unfluted barrel, but shorten it to make weight. That will increase the stiffness even further, as long a the part you cut off is the skinny part.

I've also read that cutting the flutes adds stress, and probably it does., On the other hand, making those cuts will more evenly distribute any residual stress in the barrel, so in that sense, fluting relieves stress -- I had a hard time with this one, but it too is from Dan Lilja.

So, practically speaking, you flute a barrel when (1) the rules (or "carrying effort") require a certain maximum dimension and weight, (2) you are having trouble making that weight, and (3) you absolutely don't want to shorten the barrel any further.

Or maybe (4), you like the looks, and don't care how that affects performance.
 
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