[EMS_92]

Pros and cons of each and which one would you go with?

[buckhorn_cortez]

Not an either / or question. Depends on how you expect to use the rifle. This is like asking 18-inch barrel or 24-inch barrel. For carrying it in the field all day - light weight barrel. For mixed target use, prarie dogs with a minimum of carrying for long periods of time - heavier profile, fluted barrel.

[jim243]

Depends on use, field trips where you are shooting one or two rounds at a time, then a light weight barrel. For benchrest shooting or target shooting then a heavy barrel would be better.

Jim

[Art Eatman]

In multitudes of discussions about fluted barrels, I've seen nothing definitive about any benefit. As near as I can tell, the decision has to do more with aesthetics than utility. :)

[creeper1956]

As has been stated in prior posts, without knowing what your goal is, it's hard to say which would be more advantageous. In simple terms, for a given weight... a fluted barrel will be stiffer and provide a modest improvement in heat dissipation.

Dan Lilja provides a "Contoured Barrel Weight Calculation Program" (http://www.riflebarrels.com/products/software.htm) that will compute the weight removed by fluting.

C

[EMS_92]

Sorry should of been more clear in my original post. Its for a 14.5-16" barrel on an AR15 in 5.56mm/.223

[jim243]

Sorry should of been more clear in my original post. Its for a 14.5-16" barrel on an AR15 in 5.56mm/.223

For that lenght barrel, a lightweight barrel, but stiffen it with a quadrail.

Just one person's opinion.
Jim

http://i620.photobucket.com/albums/tt284/bigjim_02/SAM_0630.jpg

Otherwise use this.

http://i620.photobucket.com/albums/tt284/bigjim_02/IMG_0481.jpg

[jmr40]

http://s1129.beta.photobucket.com/user/jmr40/media/003-6.jpg.html?sort=3&o=4#/user/jmr40/media/003-6.jpg.html?sort=3&o=4&_suid=13493786994330126006932072169

Long action Winchester FW 30-06 with a lightweight barrel. 7 lbs 8 oz as it sets.

http://s1129.beta.photobucket.com/user/jmr40/media/guns1001.jpg.html?sort=3&o=80#/user/jmr40/media/guns1001.jpg.html?sort=3&o=80&_suid=134937884746205482395202932878

Short action Winchester EW 308 with standard fluted barrel. 7 lbs 6 oz as it sets.

Both rifles are equally accurate

http://s1129.beta.photobucket.com/user/jmr40/media/targets009.jpg.html?sort=3&o=52#/user/jmr40/media/targets009.jpg.html?sort=3&o=52&_suid=1349379015084045823971059478646

http://s1129.beta.photobucket.com/user/jmr40/media/targets009.jpg.html?sort=3&o=52#/user/jmr40/media/targets007.jpg.html?sort=3&o=54&_suid=1349379015084045823971059478646

Basically the fluting helps to reduce weight to get you down to the same as a thinner weight barrel, without giving up any accuracy normally associated with lightweight barrels.

The fluting does not make your barrrel stiffer, it just reduces weight without giving up stiffness compared to a barrel of equal diameter and might help dissipate heat. I used to think it helped make barrels stiffer, but was proven wrong on that.

On a 14" AR barrel I doubt any weight loss would be noticeable. On longer, larger diameter barrels it could make quite a bit of difference.

[Inebriated]

I would get the heavier barrel on a carbine-length AR. Like jmr40 said, a barrel that short won't see much difference between the two, weight-wise.

[wgp]

For me it's never been the weight of the barrel in it's own right, it's the weight of the barrel as it affects the balance of the rifle. I have consistently found that, personally, a muzzle-heavy rifle handles better and thus a heavier barrel is my preference. The rifles I still own that have light barrels tend to be overall very light rifles that still balance well in the hands.

[taliv]

i prefer lighter. see no value in flutes. don't pretend my ARs are heavy machineguns

if you think bumpfiring is cool, have too much ammo, or use your barrel for cooking, you might go with a heavy profile

[henschman]

Assuming it will be more of a fighting carbine rather than some sort of precision rifle (based on the specified barrel length), I would go with a light profile, preferably a pencil profile. That makes the gun handle much better, and it would carry very nicely in the field. You may see some vertical stringing, but that is not an issue at all for getting hits at typical carbine engagement distances.

[Quentin]

I agree with Taliv and Henschman and prefer a pencil barrel. And it doesn't need a rail to stiffen it, I've had excellent results with standard and MOE plastic handguards on two pencils. Below is a 16" BCM LW midlength upper. (I did get rid of the ACS stock too, 14 oz vs. about half that going to a CTR!)

http://i829.photobucket.com/albums/zz211/Quentin68/DSCN1460.jpg

http://i829.photobucket.com/albums/zz211/Quentin68/DSCN1482a.jpg

[henschman]

FYI a "pencil" barrel was the original setup for the M-16, until the Marines wanted a heavy barrel for long range competition, and the Army wanted to keep it light so they could use their same underbarrel M203s, and so they came out with the bastardization known as the A2. It has a light profile barrel before the gas block, and a heavy profile after, which really doesn't do anything but add weight to the muzzle end. And this is the prized "gov't profile." An apt name, and a good example of what gov't and bureaucracy can do to a perfectly good original product.

I wish Palmetto made 20" rifles with the same "pencil" profile they offer for 16" carbines. I would be all over that.

[EMS_92]

Any specifics on heat dissipitaion and such? Im genuinely curious, since looks like the only rifle I can buy now is an HBAR due to crappy MD laws that consider anything less on an AR a regulated firearm that you need to be 21 to purchase or own. BUUUUUUT........I can always send it of to get the barrel turned down or fluted.

[Quentin]

Maryland requires you to buy the HBAR???? :eek:

Never heard of that before.

[1858]

In multitudes of discussions about fluted barrels, I've seen nothing definitive about any benefit. As near as I can tell, the decision has to do more with aesthetics than utility.

I would think that the engineers at Accuracy International gave little thought to aesthetics when they decided to flute the barrels on the AWM rifles chambered in .300 Win Mag and .338 Lapua Magnum. The AI rifles are built for serious use so I have a hard time believing that the flutes on the barrel are superfluous.

[Sniper66]

The heavy fluted barrel on my Rem 700 VSF .223. The advantage for my purpose (p-dog shooting) is that the added weight helps for shooting from a rest and shooting long distance. The disadvantage is the added weight limits it's use...no fun carrying that beast in the field. I do have to say that I haver sporter barrel and heavy barrels, which includes my fluted barrel. Overall, the heavies are more accurate, buit it may be because it is easier to keep it stable on a rest.

[Cesiumsponge]

I suspect we would get better answers on an engineering forum because adding firearms into the equation ends up interjecting a lot of anecdotal evidence, marketing, and myths. The stiffness argument would depend heavily on the actual cross-sectional area of each barrel and the fluting profile. The cooling claims from increased surface area would depend if the increased surface area results in higher radiative heat dissipaion that makes a measurable difference, and assuming it outweighs the reduction in material and reduced heatsinking ability that comes with reducing mass.

[1858]

The cooling claims from increased surface area would depend if the increased surface area results in higher radiative heat dissipaion that makes a measurable difference

What about convection?

[Cesiumsponge]

Convection too, but probably plays a much smaller role since heat dissipation by convection is most efficient with a fluid (air, liquid, etc) to move heat, like a finned heatsink. Forced convection works wonders but natural convection is pretty inefficient. Unless you're 3-gunning, convection probably won't do much for a barrel that's attached to a rifle doing benchrest, bipod, or positional shooting. Keep in mind, without actual numbers, these are all thought experiments. We probably won't ever get numbers here unless someone has the time, money, equipment, and a thought-out scientific process to run tests with identical barrels and various fluted profiles with a control barrel.

[meanmrmustard]

Me, personally, heavy/fluted.

[back40]

on a carbine, between the two, i'd liekly go with a pencil barrel.

jim243, how exactly does that quadrail "stiffen" the barrel. it's not fixed at either end. a free-floated rail would seem to make much more sense allowing barrel harmonics to be what they are where accuracy is concerned.

[jim243]

a free-floated rail would seem to make much more sense allowing barrel harmonics to be what they are where accuracy is concerned.

Exactly correct, on the varminter you will note the free floated handguard. Under the handguard the barrel is considerably heavier (wider diamiter) than that past the gas block.(24 inch barrel) and shoots 0.33 MOA all day at 100 yards.

On the carbine the quadrail attaches at the delta ring and also at the gas block making for less flex in the barrel and in my OPINION ONLY, gives it more stability and less harmonics. I don't have the equipment to test this out, as I said it is only an opinion. It has proved to be very accurate at least for me. I had thought about changing it to the lighter MOE plastic handguard, but it has worked so well, that if it isn't broke don't fix it.

Thanks
Jim

[helotaxi]

But the problem with a non-floated rail or even basic handguards on a pencil barrel is that you are flexing the barrel just by holding the handguards. Different pressures on the handguards between shots make for inconsistent barrel harmonics and different points of impact. As the barrel heats up, the effects of this get worse. The thinner the barrel the greater a positive effect a free-floated forearm will have on consistency.

As far as fluted vs. not, the numbers that I've seen (there are some around out there) showed that a fluted barrel was slightly stiffer than a straight contour barrel of the same weight, but not as stiff as one of the same major diameter. That's exactly as expected. With a good barrel stiffness and accuracy are not related when firing a load matched to the rifle. The stiffer barrel allows the rifle to shoot acceptably with a wider variety of ammo. The heavier barrel is more important for sustained firing where heat becomes an issue. The numbers that I've seen showed that if max barrel temp is used as the limiting factor and you're comparing two barrels of the same outer diameter, one fluted and one not, sustained rate of fire was essentially the same. The non-fluted barrel was slower to get to the max temp, but was also slower to cool. Over a period of time it was essentially a wash. The fluted barrel worked out to shorter strings with shorter cooling time between strings.

[Art Eatman]

My argument, what there is of it, is not about stiffness or radiation of heat. For a given weight, a fluted barrel is stiffer. And there is more surface area from which heat can radiate.

I've not seen evidence that it makes enough of a difference to matter when compared to non-fluted barrels, for group-size accuracy.

Off the cuff, a proper test would seemingly be to develop a bull-barrel rifle to its utmost quality and then average out a large number of groups. Then flute the barrel and start over, do the test-shooting and then compare group sizes.

[1858]

Then flute the barrel and start over, do the test-shooting and then compare group sizes.

But you wouldn't be comparing barrels of the same weight ... and that's the whole point. For barrels of the same weight, a fluted barrel will be stiffer. The big question is whether or not stiffness is a good thing. I think it is because the stiffer the barrel the less it deflects at rest, which in turn decreases the amplitude of the barrel when it's vibrating.

[Welding Rod]

Totally depends on your intended use.

It also depends on if it will be floated or not, and if you intend to sling up tight as a shooting aid. Or if you will be using a bipod while not floated. And what level of consistancy you will be satisfied with in your POI. And to some extent, what kind of sight(s) you will be using.

I have and prefer both light weights and HBARS for different purposes.

As the requirement for consistant POI, and the need to move decreases, a heavier barrel becomes more desireable. Also, when sling tension is being applied to an unfloated barrel, a heavier barrel becomes more desireable.

So for paper punching for groups or competing in something like high power events, heavier in generally better.

For most everything else the lighter barrels do very well, may be capable of great accuracy, especially if floated, and they are faster handling and much handier tote around.

My three favorite ARs are a 20" stainless HBAR with free float tube and Leupold Mk4 4.5x14x50, a 20" HBAR A2 that I compete with, and a 16" BCM light weight (BFH) midlength with Aimpoint M4s.

I prefer the 16 BCM LW for speed type events, and for low light conditions due to the sight.

Three ARs with competely different purposes.

My favorite all purpose AR is a 20" BCM Gov profile upper with A2 handguards and carry handle iron sights, Magpul CTR stock, and a 2-stage match trigger. I agree with previous poster that I would prefer an A1 type profile over the Gov if it were available.

[1858]

I drew up a couple of barrel models in SolidWorks last night and ran them through COSMOSExpress and was surprised by the results. I have three barrels from Krieger all of which have what Krieger used to refer to as an MTU contour but now call Varmint & Match contours. All three of the barrels are fluted. Two have 10 flutes that are 3/16" wide and approximatly 20-1/2" long. The third barrel has 6 flutes that are 1/4" wide and approximately 20-1/2" long. The .308 Win barrel on my F-Class rifle is 25" long so I used that length for the barrels shown below which have the same weight (see mass properties).

Barrel 1: 1.25" diam. for 2.75" then tapered to 0.77" at the muzzle, .308 Win chamber and .308" bore.

http://thr.mcmxi.org/engineering/barrel_analysis/308_mtu.jpg


Barrel 2: 1.25" diam. for 2.75" then tapered to 0.93" at the muzzle, .308 Win chamber and .308" bore, 6 flutes 1/4" wide and approximately 20-1/4" long.

http://thr.mcmxi.org/engineering/barrel_analysis/308_mtu_fluted_web_top.jpg


So it would appear that the fluted and non-fluted barrels have virtually the same deflection at rest i.e. 0.0045" and 0.0044" respectively, and the fluted barrel has about 18.3% more surface area. So it's probably safe to say that in this example, using an MTU straight tapered barrel, the flutes really don't do much except add cost and change the overall appearance. I have to admit that I was surprised by these results and will quite possibly omit flutes on my next barrel from Krieger. I will add that the barrel contour probably has a much greater affect on barrel stiffness for a given weight than the addition or omission of flutes. I did some barrel deflection analysis for different contours a couple of years ago and posted the results on this website. The MTU contour was quite a bit stiffer than the PALMA contour in those examples.

[EMS_92]

Nice post there, 1858. Very informative!