Anyone use fluted barrels?

[Koda_]

Used their default for Annealed 4130 steel. Wasn't happy with the annealed aspect, but didn't have time to install something else. It was a quick exercise! That alone is likely some of the unexpected numbers, but I don't think that it is the whole story.
FWIW it is rare that I use that part of SW. I'd love it if someone more familiar with that package repeated my experiment, first with the annealed 4130 and then again with 4130 at some level of HT so that we could see how the difference in HT affects the results.

You went farther that I would, good info even if material properties arent exact. The weight difference sounds appropriate, and correlates with some of the comments in this thread from those who weighed the difference.

The deflection you used is largely subjective to how you set up the simulation.... eg, put one of the flute ribs perfectly symmetrically centered on the vertical plane and on the bottom of the barrel for odd number flutes, rerun the deflection simulation pushing down and it probably will be more stiffer. That said, I don't think deflection is representative to simulating barrel harmonics... I'm not certain how one would even set that up in a CAD program. I think it would get complicated, maybe model in the chamber and recoil lug. Fix the simulation to the lug and put 60K psi on the contact area where the bolt lugs contact. I cant think of a way to simulate a bullet moving down the barrel...

FWIW, everyone interested in barrel harmonics should watch this super slo mo Bryan Litz did of barre movement when fired. Only rearward movement not any up/down.... no visible harmonics.

 

[S2r1820jc]

The best of both worlds carbon and spiral fluted

 

[Rick Richard]

The best of both worlds carbon and spiral flutedView attachment 599778

Now that's a first.

 

[Straight Shooter]

And faster heating.

But the weight difference is good to know. Ive never found a way to determine how much weight loss is from adding flutes. Half a pound is significant.

Koda, how is it faster heating?

 

[Koda_]

Koda, how is it faster heating?

less material heats faster than more.

 

[Phil Rizzo]

I've been told the wrap insulates the liner.? Holds the heat IN.
No experience to share, but I've used a heat gun on SS. Long ago

 

[Phil Rizzo]

The best of both worlds carbon and spiral flutedView attachment 599778

I bet that would give the manufacturer a Fred G Sanford heart attack.?

 

[ntsqd]

I had no intention that my 100 lbs pushing down on the muzzle was going to simulate anything that happens during the actual firing of the rifle. I just wanted something simple to gauge the relative stiffness of each barrel. I *might* get a chance tomorrow to re-run the analysis with the flutes rotated 30° so that the top of the barrel isn't a flute. That should be an interesting thing to try. The limited program available to me does not work with assemblies, only with parts. Not to mention that trying to do dynamic FEA of a barrel during firing is vastly beyond my pay grade.

The way that I modeled the flutes was that a circle concentric with the bore and tangent to the very bottom of each and every flute will measure Ø.750"

If you have a fixed amount of heat applied to something, then the resulting temperature is dependent on how much mass that something has. Generally more mass means a lower resulting temperature and less mass means a higher resulting temperature. The thermal transfer coefficient has some bearing on all of this, but it's been far too long since I had that college class and have had no need for it in work.

With a wrapped barrel there are three thermal transfer coefficients involved. That of the barrel metal, that across the boundary between the barrel metal and the CF, and finally that of the CF itself. Material boundaries don't generally tend to be very thermally conductive unless particular steps are taken to reduce the problem. Those of you who mess about with cars likely well know about the need for the thermally conducting grease that GM HEI ignition modules absolutely require or they'll cook themselves to death.Even though it's a steel (usually) module base sitting on an aluminum distributor body, the boundary between them is too insulative without the special grease in place.

 

[tim_w]

A really fast surface area experiment. Total guesses at all of the dims, but these are they:
24.00 long
Ø.308 cylindrical hole.
Ø1.06 X 2.00 long Tenon
Ø1.25 max diameter at shoulder, no straight/cylindrical section, tapers from there to muzzle
Ø.875 muzzle diameter, 90° flat crown
carbon steel
R.1875 flute "cutter"
Six straight flutes with 15° lead-in angle, Ø.750 minimum diameter (at bottom of the flutes), R3.00 transition radius, Straight portion of flute starts at 5.875 from breach and ends at 2.415 from muzzle, 25° lead-out angle with R3.00 transition radius.
I mention all of this detail in case someone else wants to see if they get the same results or not.

Unfluted it "weighs" 5.55 lbs and has a surface area of 105.02 square inches.

Fluted it weighs 4.45 lbs and has a surface area of 115.53 square inches.

By my math that is only a 10% gain in surface area. From messing around with these models it is very easy to make that number far lower as these flutes are pretty deep in a barrel contour that is pretty stout.

Next I looked at bending stiffness. I held the tenon fixed and put a 100 lbs downward force on the muzzle.
Unfluted exaggerated deflection diagram:

Fluted exaggerated deflection diagram:

Comparing the two peak deflection numbers the fluted barrel deflected down ~.06" more than did the unfluted barrel. That's roughly 60% more deflection!
I have not had time to perform a reality check on these results. I trust the process, these just aren't quite the numbers that I was expecting to see. Assuming that these results are valid this says that a fluted barrel is NOT stiffer than the same profile unfluted barrel. I was expecting that unfluted would be stiffer, but not by such a large margin.

That is two barrels of same starting mass then one barrel is fluted. Could you do the same thing but reduce the non fluted barrel total outside diameter after the tennon to equal the same mass as the fluted barrel. One the fluted barrel align the flutes so the full diametersevtions of the barrel are centered at 12 and 6. Be interesting to see the surface area comparison as well. To me these are the more practical comparisons as to me the major reason for fluting for 99% is weight reduction or more specifically maximizing stiffness and cooling for a given mass/weight.


I know Dan @ Lilja Precision Barrels did alot of modeling single beam and testing and the most significant effect on barrel stiffness is increases in diameter at the breech end and then extended forward from that point. I also has goid discussions with John Schaefer yrs ago on the same matter and he did modeling for it. He also has done extensive modeling on bolt thrust with different friction COF by changing grit polish of chamber walls down to adding a lubricant. He runs circles around me in modeling.

 

[tim_w]

FWIW, everyone interested in barrel harmonics should watch this super slo mo Bryan Litz did of barre movement when fired. Only rearward movement not any up/down.... no visible harmonics.

Researchers have been measuring barrel vibrations since around at least 1901 and known of it long before that. Not sure what Brian wrote about involving that video but if it was to show muzzle deflection movement "harmonics" vibration that was less than ideal. With cantileved beam modeling the amount of barrel vertical movement is extremely small and fast oscilations. Consider how small of movement in the vertical plane it takes to raise POI @ 0.100" of say a 24" barrel using the bolt face as pivot point and muzzle the other point. To keep it simple make the bullet traj a straight line 100yds. It is quite small measured in the ten thousandths of an inch in muzzle vertical change using the bolt face as the pivot point.

Hereis a video using triggers for ignition to trigger accelerometer sensor and for bullet exit point ensuring delineation between pore and post exit movement but can easily be differentiated on the scope.




Barrel vertical deflection and vibration/harmonics really is not debateable. Its not theroy its fact. Its been measure with lab equip many times. The issue is accurate computer modeling of it to the degree that it could consistently model it for accurate positive compensation prediction. The issue is things like stock scopes etc also oscilate and there is not just a single oscillating force. But multiples that can both build on and counter each other etc.

Some historical references:

Barrel vibration harmonics was known long before these. The ref below were looking at finding ways to model, tune it, muzzle location @ bullet exit point i.e. positive compensation.

Some references:

Untersuchungen uber die Vibration des Gewehrlaufs. Abhandlungen d. math-phys. C1 D. Akedemie Der Wissenachaften, Vol. 69, page 747-775, Munchen, 1899

"The Vibration of Rifle-Barrels", Min. of Proc. of Inst. of Civ. Eng., Vol. 191, page 217-255, 1912-13 Francis Carnegie

"On Rifle Barrel Vibrations and their Effect on the Angle of Jump", R.D. Report No. 63, 1925 Woolwich Arsenal

"The Vibrations of Rifle Barrels", American Rifleman, January 1, page 17-32, 1927 Captain Philip P. Quale

"Vibrations of a Rifle Barrel", Journal of the Royal Technical College Glasgow, Vol. 4, Part 2, page 213-239, 1938 A.E. Martin and J. Muir

"Rifle Accuracy Facts", Pub. Precision Shooting Inc. Connecticut, 1998 Harold Vaughn

"Simulation of the Vibrational Response of a Rifle Barrel During Firing", Proceedings of the Advanced Simulation Technologies Conference, organized by the Society for Computer Simulation, page 66, April 5-9, 1998 Kevin N. Schwinkendorf and Steven P. Roblye

The Vibrations of a Barrel Tuned for Positive Compensation Nov 2015
is a good brief summary of these past work and the more recent research done. 22LR makes for easy testing used there.

Using barrel vibrations to tune a barrel

This is another paper that has good descriotions of the type of testing that was done

 

[FEENIX]

I feel like carbon fiber barrels have taken over the light weight builds. Under 10 lbs.

I'm working on a 6.5 PRC hunting build with a Benchmark #5 contour straight fluted at 22"

What contours do you use?

This boils down to your intended purpose and preference. I am not a fan of fluted barrels, but I like them in bolts. If your goal is under 10 lbs hunt-ready, weigh all your components (stock, scope, rings, rail, muzzle device, and other items you will attach to your rig to hunt with, i.e., sling, bipod, etc.). Good luck!

 

[tim_w]

This boils down to your intended purpose and preference. I am not a fan of fluted barrels, but I like them in bolts. If your goal is under 10 lbs hunt-ready, weigh all your components (stock, scope, rings, rail, muzzle device, and other items you will attach to your rig to hunt with, i.e., sling, bipod, etc.). Good luck!

Yep. I can get under 10lb with scope, rings & mag but no way if you were adding a bipod etc. Not sure I would want that light of weight for a lr hunting rig. Too hard to get steady in various hunting shooting positions. Maybe with more practice and add in some yoga lol.

I like my 9-10lb rifles with scope and mag if I am packing it for distance. If I have it on my back dual strapped for a few mikes to a stand without crazy elevation changes weight really isn't a huge deal but sure do not want any of those PRS 25+lb boat anchors though. Reminds me to much of humping a minimi with full roll thru elevation.

 

[FEENIX]

Yep. I can get under 10lb with scope, rings & mag but no way if you were adding a bipod etc. Not sure I would want that light of weight for a lr hunting rig. Too hard to get steady in various hunting shooting positions. Maybe with more practice and add in some yoga lol.

I like my 9-10lb rifles with scope and mag if I am packing it for distance. If I have it on my back dual strapped for a few mikes to a stand without crazy elevation changes weight really isn't a huge deal but sure do not want any of those PRS 25+lb boat anchors though. Reminds me to much of humping a minimi with full roll thru elevation.

I agree! I was trying to find out the OP's ultimate goal because people often forget to factor it in. I know what you mean about humping through elevation gains. Below is my .270 AI with 30" Lilja barrel with sendero contour; it is 12 lbs as seen - hunt-ready. I appreciate the under 8-9 lbs rigs as I get older.

 

[806 guns]

I agree! I was trying to find out the OP's ultimate goal because people often forget to factor it in. I know what you mean about humping through elevation gains. Below is my .270 AI with 30" Lilja barrel with sendero contour; it is 12 lbs as seen - hunt-ready. I appreciate the under 8-9 lbs rigs as I get older.

View attachment 599819

This will be a hiking rifle more or less. Components should all be soon. Debating on a scope currently. Im betting it's close to the 10lb mark but the Manners eh1 really cut the weight down.