Does fluting affect barrel accuracy?

[Bart B]

I know first hand one of the reasons that Shilen is anti-fluting - Law suits - I know of a Shilen barrel that was fluted by a wanna-be-gunsmith that came apart on a customer. The wanna-be-gunsmith fluted it to close to the bore and after the second shot it came apart. We all know what happened next - law suit against the builder and Shilen. How would you respond if you were Shilen?

First, I'd get some professionals with doctorate degrees in metalurgy and mechanical engineering as expert witnesses. Then let the suit take its course and after winning, leagally pounce on the perpurtrator. How did that suit end up?

Same kind of thing happened years ago when Shooter's Choice bore cleaner first came out. Someone used it and his barrel's accuracy went south. He sued Shooter's Choice but SC proved the barrel had so much fouling in its throat and leade from being eroded away and not cleaned properly. The hardened fouling actually had kept the rifle shooting pretty accurate until it had been removed. Shooter's Choice was declared not guilty.

I watched a just-fluted Hart 30 caliber barrel have its rifled bore measured with a Sheffield air gage. The bubble wiggled as the gauging head was pushed under the back end of the flutes then move up a few tenths, then wiggled a little going by the front end then dropping back to where it started for the last couple of inches.

There may well be machining tools and techniques used today that minimally changes bore and groove diameters. I don't know all that stuff. But if one can flute any finished barrel without changing the bore dimensions, more power too them.

One barrel maker insisted that fluting increased a barrel's rigidity or stiffness. He said he had measured how much a solid blank bent down at its muzzle when held horizontally at the breech end. After fluting, the barrel drooped less. That was his proof. He didn't understand that it drooped less 'cause it weighed less. His son went to college to become a mechanical engineer so I hope the kid was able to show his dad that fluting does in fact make a barrel less rigid.

 

[durak]

First, I'd get some professionals with doctorate degrees in metalurgy and mechanical engineering as expert witnesses. Then let the suit take its course and after winning, leagally pounce on the perpurtrator. How did that suit end up?

Same kind of thing happened years ago when Shooter's Choice bore cleaner first came out. Someone used it and his barrel's accuracy went south. He sued Shooter's Choice but SC proved the barrel had so much fouling in its throat and leade from being eroded away and not cleaned properly. The hardened fouling actually had kept the rifle shooting pretty accurate until it had been removed. Shooter's Choice was declared not guilty.

I watched a just-fluted Hart 30 caliber barrel have its rifled bore measured with a Sheffield air gage. The bubble wiggled as the gauging head was pushed under the back end of the flutes then move up a few tenths, then wiggled a little going by the front end then dropping back to where it started for the last couple of inches.

There may well be machining tools and techniques used today that minimally changes bore and groove diameters. I don't know all that stuff. But if one can flute any finished barrel without changing the bore dimensions, more power too them.

One barrel maker insisted that fluting increased a barrel's rigidity or stiffness. He said he had measured how much a solid blank bent down at its muzzle when held horizontally at the breech end. After fluting, the barrel drooped less. That was his proof. He didn't understand that it drooped less 'cause it weighed less. His son went to college to become a mechanical engineer so I hope the kid was able to show his dad that fluting does in fact make a barrel less rigid.

The wana-be-gunsmith ended up paying damages - Not sure how Shilen came out of it. I'm sure it ****ed them off.... I'm going to look into having a barrel air gauged just to see.

IMHO if the barrel shoots, who cares what the rifling looks like!lightbulb

 

[Mikecr]

Well before you high five all the 'myth busting', don't overlook the builders who know what they're doing. Nor the advantages in holding an actual plan with fluting.

I can choose to run with a 7lb non-fluted barrel with a finished muzzle at 0.750"(as mentioned in the article).
Or,
I can run with a 7lb fluted barrel with a finished muzzle at 1.0", and any fluting I desire -no deeper 0.125".
With this, I'll have a 7lb barrel that's as stiff, or stiffer, than the 0.850(also mentioned), and in no way harms a bore that was lapped in this condition.

I personally doubt it would harm anything even if added later(but I don't know for sure).
And I doubt an air gauge(which provides comparative bore volume, rather than direct measure of bore/land parameters) could identify affects of this action.

Fluting is not the same as re-contouring.

 

[TXshooter]

You guys have some great thoughts on fluted barrels. I always thought stiffer and cools faster. Never thought that in order to cool faster it would heat faster to. Personally I don't care if my rifle is fluted or not. I just want it to shoot, but this is great stuff

 

[RTK]

I really don't care either way, unfortunately most of my guns shoot better than me most of the time anyway.

 

[Bart B]

I really don't care either way, unfortunately most of my guns shoot better than me most of the time anyway.

Don't feel bad about that. All of our guns shoot more accurate than we do. Put a rifle in a machine rest (accuracy cradle?) and test it's accuracy. It'll shoot smaller groups then when we hold it against our shoulder with our hands. Which is why benchresters typically shoot their rifles in free recoil; the stock's configured to a virtual machine rest that gets pushed back into battery (firing position) to the exact same position for each shot and the only thing on it that's touched by us humans is its few-ounce trigger.

Best example's when high power match rifle shooters test rifles in a machine rest such as the one below used by David Tubb and a few others:

they'll shoot inside 3 inches at 600 yards with good ammo all day long. When held by one of us slung up in prone and using aperture front and rear sights, we throw parties if all 20 record shots go inside 9 inches and most of them are inside the 6 inch X-ring. If a scope's used, we celebrate if all 20 shots go inside 7 inches and nearly all in that X-ring.

 

[TXshooter]

That thing is awesome I'd love to test one of my rifles in that thing

 

[RTK]

That would be a cool rig to put ones hunting rifles in and see just how well they would shoot, but then I would have to hang my head in shame,
Either that or give me drive to practice more.

 

[Goofycat]

Both comments from Lilja and Shilen have merit, but I see no evidence of any scientific testing that would indicate whether or not fluting is the cause of stress that would affect accuracy at long range.
Any manipulation of steel will cause stress; even shooting a bullet through the barrel causes stress on the barrel, but have there been any scientific studies by the barrel-makers that compare the final accuracy of fluted barrels with that of un-fluted barrels, using a large enough sampling of barrels so as to make any final results statistically significant?

Even if it were determined that fluting caused a loss of accuracy at long ranges, the question of how much accuracy is really affected. I.e., what difference does it really make, and is it really important if a fluted barrel is less accurate by, say, 1/4" at 1,000 yards than an un-fluted barrel. Does this piddling loss of accuracy supersede the advantages of less weight having to be carried by the shooter, plus the advantage of faster barrel cooling for those shooters who take many shots over a short period of time?

Frankly, until I see an actual study that has been completed, I remain skeptical of claims that the only good barrel is an un-fluted barrel. The advantages of a fluted barrel for general, everyday hunting are too good to blatantly dismiss. Not having seen proof either way, if I were a precision rifle-shooter at Camp Perry, I would probably go with an un-fluted barrel, just for "insurance," but this type of shooting does not involve the rigors of field hunting by those of us who have physical limitations such as bad backs, arthritis, etc., that make walking with a heavy rifle a difficult and uncomfortable chore.

 

[BountyHunter]

Bill Calfee who is a world famous 22LR BR rifle builder has written a series of articles in Precision Shooting, where he documents barrel bore variation and less accuracy of fluting and lapping that opens at the muzzle compared to the bore.

He uses lead slugs pushed thru the bores to identify and measure tight and loose spots. He proved that variances in bore dimensions decreased accuracy, at least at the BR levels.

He showed that fluting button rifled barrels opened up the bores under the fluting. Again, changes that had detrimental effects at BR accuracy levels.

He is an advocate of slighter tighter at the muzzle vs looser for extreme accuracy.

The articles ran for about a year and quite a few BR shooter put his theories to the test and found the variances. They will cut off barrels now at a tight spot even though shorter and do not flute button rifled barrels after rifling.

 

[barnesuser28]

if you are ordering the barrel directly from the manufacturer and you want it fluted why dont they flute it before they do the rifleing?

 

[Mikecr]

series of articles

More like 7 seasons of LOST..
I didn't see him actually finish with any notions beyond the well established and obvious.
As far as I know(and would have guessed), pretty much none of it applied to jacketed bullets and centerfire cartridges/barrels, as well debated at BR Central.

Slugging is to find TIGHTEST spots. It's been known since before any of us that the muzzle needs to be tightest, and either slugging or air gauging confirms this.
Tell me, what 'spot' would be chosen along 3/4 the length of a parallel fluted barrel, our barrels, to determine through measure of slug -an OPENING of bores'?

It's also well known that re-contouring affects bores with inherent stress. But this is way beyond fluting.
I doubt "quite a few BR shooter put his theories to the test and found the variances" from FLUTING.
That would mean they air gauged(rather than slugged) before and after fluting, and found issues as a direct result.
Do you know of an instance where this testing occurred?
Another reason for doubt is I have never seen fluting taken through the muzzle. It's typically stopped a few inches from the muzzle, and this would leave the muzzle tight anyway.

Known to kill accuracy is closing & reopening of a bore(opening last).
Unless fluting is perpendicular to the bore, it could only 'possibly'(if extreme) cause this with hammer forged barrels. With all others, and parallel, it would only cause opening & re-closing, at worst, which has been good for accuracy if nothing else.
Now there is potential there with contouring(reverse taper). Not much if any with mere fluting.

 

[BountyHunter]

More like 7 seasons of LOST..
I didn't see him actually finish with any notions beyond the well established and obvious.
As far as I know(and would have guessed), pretty much none of it applied to jacketed bullets and centerfire cartridges/barrels, as well debated at BR Central.

Slugging is to find TIGHTEST spots. It's been known since before any of us that the muzzle needs to be tightest, and either slugging or air gauging confirms this.
Tell me, what 'spot' would be chosen along 3/4 the length of a parallel fluted barrel, our barrels, to determine through measure of slug -an OPENING of bores'?

It's also well known that re-contouring affects bores with inherent stress. But this is way beyond fluting.
I doubt "quite a few BR shooter put his theories to the test and found the variances" from FLUTING.
That would mean they air gauged(rather than slugged) before and after fluting, and found issues as a direct result.
Do you know of an instance where this testing occurred?
Another reason for doubt is I have never seen fluting taken through the muzzle. It's typically stopped a few inches from the muzzle, and this would leave the muzzle tight anyway.

Known to kill accuracy is closing & reopening of a bore(opening last).
Unless fluting is perpendicular to the bore, it could only 'possibly'(if extreme) cause this with hammer forged barrels. With all others, and parallel, it would only cause opening & re-closing, at worst, which has been good for accuracy if nothing else.
Now there is potential there with contouring(reverse taper). Not much if any with mere fluting.

Yes Tim North at Broughton has done both and confirmed it. He air gauged and slugged one of my barrels after fluting and then relapped it but we cut off the last inch. I had to flute after rifling when we built the gun to make weight and that was only way to do it.

Plus it works just as well for jacketed by the people who tried it. Not everyone believes it and and more than a few test and keep it quiet.

You can feel tight AND loose spots and then tight again if you know what to do and how. You can mark where they start and end by slugging from both ends.

You have interesting theories on it, there is a strong reason button rifle mftrs flute and then rifle and recommend that when you ask.

Spent some time in a well known VA smith and barrel mftr that air gauges and built a lot of custom SR25 barrels for Uncle Sam after they tested his barrels and gave him $250K to buy new machinery to meet their demands. Air gauging is interesting and he would allow you to bring your barrels to test them.

 

[Bart B]

While fluting does indeed induce stress, if one wants a light weight accurate barrel for hunting instead of a heavier one, consider the following.

A 22 inch long 2.1 pound light weight 30 caliber barrel .600 inch at the muzzle's just as stiff as a 26 inch long 4.4 pound medium weight one with muzzle diameter at .700 inch. They both are equally stiff and have the same resonant frequency they vibrate at when screwed into a receiver. Both can have the same accuracy albeit the shorter one will shoot the same bullet out about 80 to 100 fps slower with the same peak pressure.

When aftermarket barrels became popular for service rifles, folks began having button rifled blanks contoured for both M1 and M14 rifles. None of them shot all that well. But when the blanks were contoured before gun drilling and rifling, they did very well indeed. I think Barnett, a smith in Virginia had Douglass make barrels for sale to the US Army rifle teams this way. And they were great.

Other folks tried turning down Hart button rifled barrels to reduce weight in bolt guns and they never shot as accurate afterwords.