Spiral flutes, straight flutes, or bull barrel

[NorthBorder]

Looking at a rifle that has a spiral flute, a Savage 17hmr. As far as the performance of the rifle goes do straight flutes vs spiral flutes vs a bull barrel affect that performance?
Being a rimfire shooting 5 or 10 rounds in quick succession wouldn't heat the barrel up significantly, I wouldn't think, to cause the groups to open up.
Just curious what your thoughts are on the subject and you may opine about the worth or value of the fluted barrelled 17hmr.
This particular model is a Savage 93R17 BJR. It does have a cool factor but is that worth the extra $75-$80?

 

[JohnKSa]

No performance difference for spiral vs. straight.

If heating is an issue the fluted barrel might dissipate heat a little faster than an unfluted barrel, but not much faster.

All else being equal, a spiral flute removes more metal than a straight flute, so it will be a little lighter and might dissipate heat a little faster.

The primary benefits of fluting are:

1. For a given barrel diameter, a fluted barrel will be lighter, all else being equal.
2. For a given barrel weight, a fluted barrel will be stiffer, all else being equal.

 

[Steve S.]

Select the barrel configuration you like; you will not notice a perceivable difference - splitting the hair of a split hair - in the aesthetic category, there may be a big difference for you, in the performance category there will be no difference. The largest variable affecting accuracy is the person doing the shooting.

 

[cfullgraf]

The ability of a barrel to shed heat is directly related to the area if the cooling service that is available.

So, a straight fluted barrel will shed more heat than an unfluted barrel and a spiral fluted barrel will shed more heat than a straight fluted barrel.

How much improvement? Not much as the amount of additional square inches exposed for cooling is relatively small when compared to other configurations.

As a note, the Lewis machine guns mounted on aircraft during WWI had a finned cooling sleeve on the barrel to enhance cooling. Lots of extra surfaces to improve cooling.

WWI Ground mounted heavy machine guns had water cooled cooling jackets to keep the barrels cool. Again, an improved cooling system.

Remember, fixed machine gun installations were not concerned with MOA accuracy, just the amount if lead unleashed into the air. The “shotgun” effect of a machine gun put enough lead into the air to be lethal.

With hand held hunting rifles, fluting affords some additional cooling but not much. There are some cooling aids available for hunting rifled (fans that blow air through the bore, etc) that aid with barrel cooling but the improved cooling is not much.

I have a 17 Rem bolt rifle with a fluted barrel that the grouping goes to pot in 3 or 4 rounds. Probably a round or so better than an unfluted barrel but I still need to watch the number of rounds put through the gun to maintain accuracy.

Fluting barrels look cool and can provide small increments of effectiveness. One has to decide if it is worth it for them.

I’m passed my fluting stage these days.

 

[jmr40]

It's mostly about weight and aesthetics. A bull barrel weighs more, is the stiffest and theoretically the most accurate. I don't think it's enough difference with rimfire cartridges to matter in mechanical accuracy. With centerfires yes. A heavier barrel might be easier for the trigger puller to shoot it more accurately.

Fluting the barrel is a compromise where you can start with a heavy barrel and remove weight without significantly changing accuracy compared to a heavy barrel. If I want to keep weight down, I'd much rather have a large diameter barrel that is fluted than a much lighter weight mountain rifle barrel profile.

Fluting some barrels makes little differene. Tikka offers a fluted barrel, but their barrels are already pretty thin. It doesn't remove enough metal to be noticeable. The Ruger American Gen II rifles have deep spiral fluting on a pretty thick barrel. It makes a significant weight difference on that rifle.

Spiral flutes can be longer, removing more metal than straight flutes.

Fluting will help the barrel cool faster. It's science, but how much it helps is debatable. It's not something that I take into consideration.

And some people think they look cool. I do, especially with spiral flutes.

I wouldn't pay to have an existing barrel fluted but given the option to buy a factory fluted barrel that's what I'd do

 

[Slamfire]

You will see more inaccuracy due to the ammunition than you ever see from the external configuration of your barrel.

 

[CraigC]

In a rimfire it's more about aesthetics and a wee bit of weight savings than anything. I don't find the Savage rimfire bull barrels to be too heavy to carry all day. Really boils down to preference. I think the spiral fluted blued rifle looks pretty good.

 

[Crosshair]

As a note, the Lewis machine guns mounted on aircraft during WWI had a finned cooling sleeve on the barrel to enhance cooling. Lots of extra surfaces to improve cooling.

The fins were often removed for aircraft use to reduce weight. They weren't needed when you had a constant 80+ mph flow of air. Though plenty of unmodified Lewis guns were indeed used on aircraft. Even with the 94 round magazine, the barrel wouldn't overheat on an airplane without the cooling fins.

 

[Anchorite]

You will see more inaccuracy due to the ammunition than you ever see from the external configuration of your barrel.

Amen.

 

[catnthehat]

Years ago I asked four really well known target rifle gunsmiths about flutes and the answer was always the same .
Basically , fluting looks cool but really doesn't factor into cooling enough to make a difference!
Cat

 

[Armorer 101]

The fluting type is a non issue if done by the factory, regards any real discernible difference in accuracy. But the 17 rimfire is notorious for fouling a bore very fast, just to start with, and that has nothing to do with fluted or non fluted barrels. If you think you can shoot a 17 and not scrub the bore, every few rounds, you might go with a 22 LR.

 

[doubleh]

My experience is that fluting is for looks. Neither of my 17HMR's have ever had fouling problems.Maybe I don't shoot them fast enough to cause any.

 

[tark]

2. For a given barrel weight, a fluted barrel will be stiffer, all else being equal.

But why? I have never seen or heard any explanation on exactly WHY this is true.!!! How does removing metal from a barrel, by cutting grooves in it, either longitudinally or in a spiral, somehow make it stiffer?? I suspect I might ( will ) receive an avalanche of responses to my question. Please give exact scientific reasons, and evidence, proving this is true.

Because I think it is just an oft repeated myth...

 

[JohnKSa]

You are correct that if you start with two identical barrels and remove metal to flute one of them, the one with the metal removed will be less stiff. The key is that it will also be lighter.

It's important to focus on the phrase "for a given barrel weight" for the rest of the statement to be true. For a given barrel weight, the fluted barrel must have a larger diameter and that will make it stiffer.

 

[JDeere]

See jmr's Post #5 for the answer in a nut shell...

 

[Weflyfast]

Not true- an I beam is "stiffer" than a solid bar stock.... the shape is a factor.....not just the amount of material-
Look in your Machinery Handbook!
Shape and finish will reduce K factor.....

 

[JohnKSa]

You are definitely correct that shape is a factor, but there are limitations to what it can do.

An I-beam is stiffer than a solid bar of the same cross-sectional area. If you have a bar of the same outside dimensions as an I-beam, the bar will be stronger--it will also be heavier (more material) and have significantly more cross-sectional area. Think about it. The bar of the same outside dimensions as an I-beam will have the I-beam contained within it plus some extra steel besides. Obviously adding extra steel to an I-beam can't make it weaker.

Note that in this source, what is always compared is two beams of the same cross-sectional area (same amount of material), not two beams of the same outside dimensions.

I Beam Strength

Steel is the most-used metal in construction today. I beam strength can withstand the elements and bear significant weight loads.

www.bushwickmetals.com

On the surface, you might think that a solid steel beam would be the strongest option. The truth is that i-beam strength is greater, particularly when you consider that the same cross-section can bear more weight when sculpted into an “I” shape.

Imagine an i-beam and a solid beam with the same cross-section. Because an i-beam is rolled into that “I” shape, the i-beam will have more flange surface area than a solid beam. For the same amount of steel used and the same overall weight, you’ll get a higher load-bearing capacity and a high moment of inertia with an i-beam because of its ability to redistribute that weight.

As we’ve already mentioned, an i-beam with the same cross-section as a solid beam is going to be larger and capable of bearing more weight.

 

[Varminterror]

How does removing metal from a barrel, by cutting grooves in it, either longitudinally or in a spiral, somehow make it stiffer??

When comparing for equal WEIGHT, that material removed from the flutes would be replaced between the flutes, creating a larger cross-section, in other words, a larger diameter barrel.

I shared some details, approximating the math for a Savage 12 I own to describe the influence of weight, diameter, surface area, and stiffness comparison between this fluted barrel and non-fluted barrels of the same weight and alternatively the same diameter.

 

[Varminterror]

For what it is worth - a comparison I can mention for 22LR versions of this same action: I have a Savage Mark II BSEV I restocked into a Boyd’s ProVarmint stock which has the fluted heavy barrel and my son has a Mark II FSS which has a THIN standard Sporter barrel, also restocked into a Boyd’s ProVarmint stock, and discounting the difference in shootability (balance and tracking of the heavier, more forward balanced rifle vs. the lighter, more centrally balanced model), the two shoot too similarly for me to truly claim one more accurate than the other.

 

[burrhead]

I don't think the flutes do much of anything but they look cool, Here's mine.

 

[Walkalong]

I don't think the flutes do much of anything but they look cool,

Yep.

 

[22250Rem]

Yep.

Wish I had a pic of the CZ -USA web site page from late 2016 where they admitted that the flutes on the CZ-455 Varmint Laminated Thumbhole fluted in 22LR were basically just there for looks. Especially in a 22LR platform, but I have always been a fluted barrel fan and that helped push me into that model of the 455 series back in January 2017. Don't see very many fluted barrels on rimfires, or at least I don't. .. ..

 

[tark]

You are correct that if you start with two identical barrels and remove metal to flute one of them, the one with the metal removed will be less stiff. The key is that it will also be lighter.

It's important to focus on the phrase "for a given barrel weight" for the rest of the statement to be true. For a given barrel weight, the fluted barrel must have a larger diameter and that will make it stiffer.

Now I'm happy! This makes sense to me.

See jmr's Post #5 for the answer in a nut shell...

I did. See above.

 

[MikeInOr]

Looking at a rifle that has a spiral flute, a Savage 17hmr. As far as the performance of the rifle goes do straight flutes vs spiral flutes vs a bull barrel affect that performance?
Being a rimfire shooting 5 or 10 rounds in quick succession wouldn't heat the barrel up significantly, I wouldn't think, to cause the groups to open up.
Just curious what your thoughts are on the subject and you may opine about the worth or value of the fluted barrelled 17hmr.
This particular model is a Savage 93R17 BJR. It does have a cool factor but is that worth the extra $75-$80?
View attachment 1251306

Fluting removes weight which also removes thermal mass. The greater the thermal mass of the barrel the more shots it will take to heat the barrel up by a set number of degrees. It is thermal expansion of the barrel that causes the poi to change. So I would expect a bull barrel to have less temperature rise in 10 shots, meaning less thermal expansion of the barrel meaning a theoretically more accurate barrel in the 5 to 10 shot string with a lengthy waiting period in between strings situation described by the OP.

 

[CraigC]

I don't think the flutes do much of anything but they look cool, Here's mine.

View attachment 1251611

I've either never seen or never noticed the blued, spiral fluted model. I've seen the stainless version but not the blued one. I'm digging it!