I'm planning on buying a Bushmaster 20" national match HBAR upper and i'm wondering if i should get it fluted or not. I plan on mainly target shooting, I might take it hunting some day. I only have a budget for one rifle in the near to midterm future is so I'm wondering what the best overall option is.

I think that fluting helps cooling and that's it...  Sounds like the kind of shooting you're gonna do don't require cooling... I would leave it off... Open for disagreement!

Flute it.  What's $50.  Cooler, lil' lighter, and some say it increases barrel strength.  How can one go wrong?

I pulled this off the Bushmaster.com Knowledgebase:


[i]Fluting (machining lengthwise grooves into the outer surface of the barrel) increases the surface area of the barrel - thereby allowing increased radiational cooling of the barrel mass. This process also adds to the "stiffness" of the barrel which enhances its accuracy. A third benefit of fluting is that the barrel is lighter after machining removes the steel in those lengthwise grooves. A fluted barrel will last longer, shoot straighter, and is considerably lighter than a standard heavy barrel. The accuracy gains would be most noticeable at longer distances or to the competition shooter, but for only $50 additional for most Bushmaster barrels, many feel that the benefits of fluting are well worth the cost. [/i]

I literally JUSSSTTT came back from sending my M4 barrel to be replaced with a fluted 16".

[url]http://www.ar15.com/forums/topic.html?b=3&f=118&t=169191[/url]

GO FOR IT! it's only 50 bucks, thats only a fraction compared to the price you're going to pay for the rilfe all together, and it will last you a lifetime! And by the way, there is nothing cooler looking than a fluted barrel...[:D]

hmm, might have to look into that for myself

ArmaLite's position is that fluting adds nothing.  Now there is always the 'cool' factor to consider !!

I'm not saying that you're lying or anything, but i think armalite must be severly confused on something.
The [b]least[/b] it has to add is a lighter barrel. I know for a fact its about .5lbs lighter on a 20" barrel
Also, why would most sniper/match rifles be fluted? Take accuracy international for example. Often you will see .50BMG barrels fluted for weight and heat reduction purposes.
But thats just what i think.
LCF all the way though....

80% more surface area for cooling purposes.  More like 81%, but who's counting.

[image]http://home.earthlink.net/~orangeneck/images/BM16A3KKF2.jpg[/image]
I am with the cool factor and the functional factor.

Oooooooo who did your fluting??? very very nice!

The coolness factor is always fun.

[img]http://home.quixnet.net/~mcress/flute.jpg[/img]

Here's a relevant thread I started a while ago:

[url]http://www.ar15.com/forums/topic.html?b=3&f=118&t=169166[/url]

dang slumlord, thats something i've never seen.  is that yours?  if so, was it yours before it was fluted & why did you flute it? weight/cooling/coolness factor??? did you notice a difference in weight after the fluting was done?  

the coolness factor on that thing is off the scales, indeed!  

*looks at barrel and begins deep thought*

Ok Fluted it is. The coolness factor is just too much for me. Thanks

I wonder if Kurt would do the barrel between the front sight tower, then get a PRI. Ugh...Damn it.
*Waves bye to his check*
-Steve

I think I am sold on this. That fluting goes all the way to the upper receiver, correct? Anyone have photos of a 20" fluted HBAR w/o handguards?

Lockedoff,
why don't you explain things to ArmaLite ??  I'm simply reporting their position on this subject.

[b]Now back to that 'COOL' factor............[/b]

I really don't like fluted barrels on AR's, but I must say that M-4 barrel looks supa kewl!!

In my experience, fluting decreases accuracy very slightly, increases heat dissipation, decreases the barrel weight by about 1/2 pound, and makes the barrel heats up faster.

In short, it does about the same thing as the M4/MA16A2 profile barrels, but with only half of the weight savings.

We are not saying that it is not cool. I personally think it's very cool. We just have different views about what it does. We have people that have fluted barrels then want hand gaurd weights because it's to light. We will stick to making a top of the line rifle and you guys can do whatever you want to them. There are enough people that can do these things in the aftermarket side of things that we will let them because most of them do a fabulous job  

It's a BM factory job. Though, I believe Slumlord's flute job is way cool. The comp was installed by KKF.

Glad you like it.  The barrel was fluted this way when I bought it, one of the biggest factors of that upper.  

Here is the rest of the barrel.
[img]http://home.quixnet.net/~mcress/barrel%20flute.jpg[/img]

Here is the whole rifle.
[img]http://home.quixnet.net/~mcress/whole.jpg[/img]

And i'm doing is reporting my position on their position[}:D]

btw: lol at Lockedoff[;)]

I haven't finished all tests but so far a 26" fluted barrel from bushmaster is not heating up as fast as it un-fluted twin does. I have to borrow the skin thermocouples from the lab at work and we have had hand guard differences that my brother and I are still arguing about. I can say the fluted barrel can do 25 and 50 rounds and have it's temp back down quicker.

I'm a reasonably experienced gun guy, an AR-15 novice  BUT I know my physics and unless the AR is different from everything else in the universe, here is how it works.

Strength:
Fluting an existing barrel, makes it lighter and weaker.  Removing material from a barrel makes it weaker, period.  There is no voodoo magic that makes it possible to make something stronger by removing metal.

With that said, however, it is possible to make a fluted barrel both lighter and stronger than a comparable non-fluted barrel.  But you have to start with a larger blank.

The trick to making a tube strong is to have material around the periphery.  

I'm pulling these numbers out of my ear to illustrate a point, so work with me.  

If you have a 1" barrel  and flute it, it is possible for the resulting barrel to be both stronger and lighter than a non fluted 3/4 inch barrel.  The idea is that the fluted barrel is geometrically stronger.  

Think of it this way.  You have a 3 lb steel rod that is 18" long and solid all the way through.  Next you have a 3 lb steel tube that is also 18" long.  The wall thickness can be whatever is necessary for it to end up at 3lbs.

Which is more rigid.  Obviously, the tube is more rigid than the rod, because it has more metal around its periphery.  

I hope this makes some sense.

Regarding heating and cooling.

There are 2 forces at work here.  

1) Thermal Mass
2) Surface area

Fluting a barrel reduces its thermal mass, so it will heat up faster.  A given amount of thermal energy has less metal to heat, so it heats it more.  But it increases its surface area, so it will cool off faster also.  

The bottom line is that a fluted barrel will heat up faster initially, but will eventually reach a point where it runs cooler than a non fluted barrel.  Its increased surface area means it can transfer heat to the air faster than a non fluted barrel.  

So . . in summary.  If I was concerned about weight, I'd try to get  a large diameter fluted barrel.  In reality, if we weren't told what we were shooting, we couldn't tell the difference.  So I guess the real issue is: do you think it looks cool and is worth the extra $.  Either way, you won't get hurt.

I hope this makes sense to all of you.  If you want any clarification feel free to write.  

Best regards,

Don

This has been on of the better "fluted barrel" discussions.

If the choice was between a fluted and an HBAR. I'd go fluted ALL THE WAY.  HBARs are just too heavy.

It would be a harder choice between a fluted and a low profile barrel. In which case I would have to conclude by getting both. Which I did.

My super UNscientific tests seem to agree with mcgilbery. The fluted gives you an edge in weight, and seems to handle heat very well. I have not noticed any decrease in accuracy, and would have to say because of the heat handling capability that the fluted would give "slightly" more consistant accuracy with prolonged shooting (especially over a low profile barrel). This is purely conjecture and deductive reasoning.

I love em all!!

Edited to add: Good post dnmdcm, Welcome aboard!

Edited again to add: Slumlord that is one SWEET barrel.

From the Shilen barrels website...
"Fluting is a service we neither offer nor recommend. If you have a Shilen barrel fluted, the warranty is void. Fluting a barrel can induce unrecoverable stresses that will encourage warping when heated and can also swell the bore dimensions, causing loose spots in the bore. A solid (un-fluted) barrel is more rigid than a fluted barrel of equal diameter. A fluted barrel is more rigid than a solid barrel of
equal weight. All rifle barrels flex when fired. Accuracy requires that they simply flex the same and return the same each time they are fired, hence the requirement for a pillar bedded action and free floating barrel. The unrecoverable stresses that fluting can induce will cause the barrel to flex
differently or not return from the flexing without cooling down a major amount. This is usually longer than a shooter has to wait for the next shot. The claim of the flutes helping to wick heat away faster is true, but the benefit of the flutes is not recognizable in this regard until the barrel is already too hot."

I think it is stupid.

[url]http://www.jobrelatedstuff.com/forums/topic.html?b=6&f=5&t=169988&w=searchPop[/url]
[url]www.jobrelatedstuff.com/forums/topic.html?b=3&f=118&t=157057&w=searchPop[/url]

and NO it does not:
1) make your rifle cooler
2) significantly help with cooling
3) make the barrel stronger
4) make the rifle more accurate

Kicker9898 brings up another point I forgot.  That fluting, after the fact introduces stresses into the barrel.  

The "right" way to flute a barrel is to flute the blank, then stress relieve it, then bore it out and rifle it.  

That is most likely not how most companies flute their barrels.  Most likely, a finished barrel is fluted.  This introduces the stresses and inacuracies that kicker9898 mentioned.  

With that said.  it looks cool and if you use your ar to shoot cans at 50 yards, then go for it.  But its not something you'd to to a prarie dog gun.

Don