# Rifle Barrel Fluting



## thestelster (Feb 5, 2022)

I'm just setting up the milling machine to flute a rifle barrel.  30" stainless barrel, .338 Lapua, 10 flutes, 20" flute length, using a 3/16" convex cutter.


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## DPittman (Feb 5, 2022)

Keep us posted and educated on the process.


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## thestelster (Feb 5, 2022)

Barrel is between centers. Since I'm using a side milling cutter, the side of the barrel surface has to be parallel with table movement.  Less than a 0.001" over 20", that's good.  Now to adjust the supports to make contact with the barrel and lock them down.


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## DPittman (Feb 5, 2022)

thestelster said:


> Less than a 0.001" over 20"


Wow, I'm not sure I could achieve that sort of accuracy.  
This is just for the outer flutes on a barrel right?  Why would it need that sort of accuracy? Is it because the lines would visually exaggerate or show the discrepancy?


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## thestelster (Feb 5, 2022)

DPittman said:


> Wow, I'm not sure I could achieve that sort of accuracy.
> This is just for the outer flutes on a barrel right?  Why would it need that sort of accuracy? Is it because the lines would visually exaggerate or show the discrepancy?


It's easy enough to do.  Just takes a little patience.  In reality, it doesn't need to be that accurate, but your getting close to the bore, so its better to be prudent, and be as precise as possible.


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## thestelster (Feb 5, 2022)

Everything is set up, tightened down, speed set, rotary table at zero.  Depth of cut 0.085", speed 100rpm, feed 3 ipm.  Here goes.


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## thestelster (Feb 5, 2022)

Finished flute #1.  Remove top support bar, unlock rotary table advance to 36°.  Lock up cutting flute #2.  At 3ipm, 20" cut.  Approximately 7 minutes per flute, x 10 flutes =70minutes cutting time ,and several hours set up time!!


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## thestelster (Feb 5, 2022)

Going on fluke #5.  Up to now, I haven't had to adjust the support fingers, because they were against the smooth barrel, but now that we have rotated the barrel 180°, the horizontal jaws will be against a flute, so I have to loosen them off, make them touch.  The vertical jaws are still on smooth barrel surface, so no need to adjust them yet.


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## thestelster (Feb 5, 2022)

Also, after every flute cut, I unlock the tail stock and readjust.  As the barrel gets hot, it lengthens, so you have to accommodate for that.  And if you take a break and it cools, it shrinks, adjust accordingly.  And that's here on the mill or on the lathe too.  If you don't, the part can warp.


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## DPittman (Feb 5, 2022)

Looking good.


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## PeterT (Feb 5, 2022)

That's cool. Newbie question but do the flutes have a specific function or mostly aesthetics? You mention stainless, what is the actual alloy?


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## Dusty (Feb 5, 2022)

PeterT said:


> That's cool. Newbie question but do the flutes have a specific function or mostly aesthetics? You mention stainless, what is the actual alloy?



Not being a gun smith I would think the flutes reduce overall weight while maintaining accuracy and strength, likely helps to cool the barrel somewhat like a heat sink.


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## thestelster (Feb 5, 2022)

Done.  Now to go walk the dog.  Then get off my aching feet and have a bourbon.


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## thestelster (Feb 5, 2022)

PeterT said:


> That's cool. Newbie question but do the flutes have a specific function or mostly aesthetics? You mention stainless, what is the actual alloy?


Dusty is correct.  The most important aspect of fluting is that it creates a greater surface area, therefore it will dissipate heat quicker.  Also, the barrel is stiffer compared to one of the same weight.  And it looks cool.


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## 6.5 Fan (Feb 5, 2022)

So next time spiral fluting?


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## thestelster (Feb 5, 2022)

6.5 Fan said:


> So next time spiral fluting?


Haha, I'd love to have the helical index gearing/mechanism to do that old school!!  As opposed to CNC.


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## thestelster (Feb 5, 2022)

PeterT said:


> That's cool. Newbie question but do the flutes have a specific function or mostly aesthetics? You mention stainless, what is the actual alloy?


I believe most barrel makers use 420 or 416 stainless steel.  They are slightly magnetic, and will rust as opposed to your stainless pots and pans.


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## Degen (Feb 5, 2022)

The biggest danger in fluting is accidentally hitting a harmonic resonance to your preferred load.  That happens accuracy goes out the window.  Hit it right and your groups tighten.

Question becomes do you take this into consideration when you set up your flutes and if so any hints you wish to share?


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## PeterT (Feb 5, 2022)

I'm interested in your rotary table / chuck setup. The jaws are removed & the dog is in the T-slot? I assume you have an MT dead center passing through the chuck bore hole & into the RT socket, or??? is it an integrated chuck style? (Guess I'm just wondering what the purpose of the chuck is in this operation as opposed to completely removed ).

The picture with the cap screw, is that to provide hold down clamping to the barrel on either side of cutting action, or?

Is the barrel rough bored or finish bored or no bored at this point?


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## thestelster (Feb 5, 2022)

Degen said:


> The biggest danger in fluting is accidentally hitting a harmonic resonance to your preferred load.  That happens accuracy goes out the window.  Hit it right and your groups tighten.
> 
> Question becomes do you take this into consideration when you set up your flutes and if so any hints you wish to share?


Harmonic resonance happens no matter if the barrel is fluted or not, thick or thin, long or short, they all resonate, and they will all have different nodes and anti-nodes.  That is one of the prime reasons to handload:  to work up a particular load which is the most accurate with your barrel/action/stock combination.  You are trying to work up a load so that you end up with a resonant node (minimum amplitude) at the point of bullet exit.  Browning created the BOSS* Ballistic Optimizing Shooting System, *which was a muzzle brake that you were able to move forward or back to try to align the resonant node to the bullet exit.  So if you did not handload and used factory ammunition, the best device was the BOSS, or the equivalent.  But, of course you would have to readjust it if you switched ammunition, or even sometimes different lots of ammunition.  So the answer to your question, is no.


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## thestelster (Feb 5, 2022)

PeterT said:


> I'm interested in your rotary table / chuck setup. The jaws are removed & the dog is in the T-slot? I assume you have an MT dead center passing through the chuck bore hole & into the RT socket, or??? is it an integrated chuck style? (Guess I'm just wondering what the purpose of the chuck is in this operation as opposed to completely removed ).
> 
> The picture with the cap screw, is that to provide hold down clamping to the barrel on either side of cutting action, or?
> 
> Is the barrel rough bored or finish bored or no bored at this point?


Hi Peter, when I order barrels, I specify the bore/groove dimensions, twist, contour and overall length.  They are match grade single cut rifled and lapped.  On my end I will thread, chamber, cut crown, engrave caliber designation, polish, and bead blast (stainless), or blue (chrome moly), flute if requested, or machine to octagon, or what ever the customer wants.

In regards to the rotary table.  It has a 6" Bison three jaw chuck mounted.  The table does take a MT2 centre which I am using.  I don't bother removing the chuck, its accurately centered, so why bother removing it.  Most of the times I can still have the jaws in place but opened up, and the centre in.  I just had the jaws removed from the last job I did, and hadn't bothered to put them in.  Why don't I chuck the barrel shank in the three jaw then, you might ask.  Well the accuracy of a decent three jaw is at minimum 0.002" at about 2" out,  but if the barrel is 30" long, I could have as much as 0.030" run out at the muzzle.  No thank you.

That cap screw is there just to keep a little downward tension on the bottom support jaw.


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## YYCHM (Feb 5, 2022)

That was a contoured BBL that you fluted?


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## LeakyCanoe (Feb 5, 2022)

thestelster said:


> Then get off my aching feet and have a bourbon.



OK, you've raised a trout here .  I've become a convert over to bourbon lately.

Not intending to hi-jack your thread or anything, but _*what's your tipple of choice* _if you don't me asking ?  I'm still trying to figure it out. In fact I am still data-testing right now as I type this !

Here's a photo of my own personal pandemic lab experiment underway from last summer that I sent to a buddy....I tried to kick it up to just beyond "entry level" and look to separate out the corn from the tassel on this whiskey category.  Don't make any impressions from the amount in each bottle...they weren't all bought together at the same time !   

And you know what ?   I am having trouble thinning the herd in that price-range I am finding.           

_Sigh_...so may rabbit-holes in life to explore.


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## thestelster (Feb 5, 2022)

YYCHM said:


> That was a contoured BBL that you fluted?


Hi Craig, yes.  That was contoured.  Generally, I always order them contoured, unless I have to do something weird like integral projections such as (quarter rib, sight base, full length, rib, second recoil shoulder, sling swivel stud).


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## PeterT (Feb 5, 2022)

thestelster said:


> Why don't I chuck the barrel shank in the three jaw then, you might ask.  Well the accuracy of a decent three jaw is at minimum 0.002" at about 2" out,  but if the barrel is 30" long, I could have as much as 0.030" run out at the muzzle.  No thank you.


You'll notice I didn't ask that question because I knew better LOL. I typically have a 4J chuck on mine for that reason, but it's not always the best way either depending on the job. If you have established centers, best to use them. Coincidentally I was just pondering how to integrate a low profile dog on the RT T-slot with MT dead center. I have these crappy offshore forged affairs intended for lathe work, but I think I can make something better.


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## Degen (Feb 5, 2022)

thestelster said:


> Harmonic resonance happens no matter if the barrel is fluted or not, thick or thin, long or short, they all resonate, and they will all have different nodes and anti-nodes.  That is one of the prime reasons to handload:  to work up a particular load which is the most accurate with your barrel/action/stock combination.  You are trying to work up a load so that you end up with a resonant node (minimum amplitude) at the point of bullet exit.  Browning created the BOSS* Ballistic Optimizing Shooting System, *which was a muzzle brake that you were able to move forward or back to try to align the resonant node to the bullet exit.  So if you did not handload and used factory ammunition, the best device was the BOSS, or the equivalent.  But, of course you would have to readjust it if you switched ammunition, or even sometimes different lots of ammunition.  So the answer to your question, is no.


I was aware, there are a few formulas I've seen years ago, that help keep you away from the blunder.


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## YYCHM (Feb 5, 2022)

LeakyCanoe said:


> OK, you've raised a trout here .  I've become a convert over to bourbon lately.
> 
> Not intending to hi-jack your thread or anything, but _*what's your tipple of choice* _if you don't me asking ?  I'm still trying to figure it out. In fact I am still data-testing right now as I type this !
> 
> ...



Try a good Scotch some time.  You will convert


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## thestelster (Feb 5, 2022)

LeakyCanoe said:


> OK, you've raised a trout here .  I've become a convert over to bourbon lately.
> 
> Not intending to hi-jack your thread or anything, but _*what's your tipple of choice* _if you don't me asking ?  I'm still trying to figure it out. In fact I am still data-testing right now as I type this !
> 
> ...


Ahh Mr. Canoe, a man after my own heart.  I will be completely honest.  My single most adored fire-water is Lagavulin single malt Scotch. I absolutely adore this whiskey.  I do not like many other scotches, but Lagavulin I adore.  Saying that, I cannot afford it.  I have been looking around for a good tasting whiskey that doesn't break the bank.  I locked onto Jamison's Irish whiskey.  That I like very much but always looking for something else.  I think some ancient Greek philosopher once said, "Variety is the spice of life", or could have been Italian, or English??  I decided to try some bourbon.   Jack Daniels was way too sweet.  But Woodford Reserve, which you have in your collection is absolutely wonderful.  But is also a little pricey.  My current drink is Bullet 10year, which you also have.  I like this very much.  It has a bit of sweetness, no bitterness, or aftertaste, and is very smooth.  I've also had the Markers Mark which I did not like, and the Elijah Craig which was good, but not great to my palette.  If you have a suggestion, I would love to hear.


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## thestelster (Feb 5, 2022)

PeterT said:


> You'll notice I didn't ask that question because I knew better LOL. I typically have a 4J chuck on mine for that reason, but it's not always the best way either depending on the job. If you have established centers, best to use them. Coincidentally I was just pondering how to integrate a low profile dog on the RT T-slot with MT dead center. I have these crappy offshore forged affairs intended for lathe work, but I think I can make something better.


Hi Peter, I hear ya regarding the lathe dogs.  Even though the one I am using there is for the lathe, I've cut the tail off short for use in these jobs.  I use the rotary table with the three jaws for making octagon or square parts, or small short pieces.


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## thestelster (Feb 5, 2022)

Degen said:


> I was aware, there are a few formulas I've seen years ago, that help keep you away from the blunder.


Hi Degen, you mean you've seen a formula that determines fluting dimensions for a particular barrel contour?  That would be amazing, and probably extremely complicated?  If you could dig it up I would love to have a copy.


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## Degen (Feb 5, 2022)

More so on tapers than fluting, was about 25-30 years ago.  I suspect though that there are some as these would be similar to column design in civil (my field of study in Uni) and the same concepts are used in mechanical.

Old school its a bit more of black art .


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## PeterT (Feb 5, 2022)

thestelster said:


> On my end I will thread, chamber, cut crown, engrave caliber designation, polish, and bead blast (stainless), or blue (chrome moly), flute if requested...


I'd like to see your bead blasting & blue-ing when the opportunity arises, please & thanks.
What about heat treating, do you have your own shop facilities?


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## LeakyCanoe (Feb 5, 2022)

Scotch is just OK to me...it's my wife's choice of whisky, but I always preferred dark rums after getting exposed to those on trips to the Caribbean.  Of the Scotch I've had, I like the nicer _Abelour _the best of all.  The rest I generally find harsh or crazy peaty.  Bourbon is now my new fave.  And I think it is because of the underlying sweetness.

I really have a hard time pulling a leader out of that grouping I sent.  Those were all LCBO purchases, that being pretty much the extent of my booze shopping universe since the pandemic began.  So Doug Ford won't be happy to hear that with the border beginning to open up that I have been back over into the U.S. again.   _BAM ! _   The selection, even at Duty-Free on the way over when I picked-up a bottle of 4 Roses, offered up considerable new choices in the price notch just up from that grouping.  And we're not talking Pappy Van Winkle or even $ 100+/ bottle stuff.  Apparently all the hipsters have discovered it too, along with me...so the selection is absolutely stunning there.

What I've decided just in the last month or so is that bourbon to me is like zip-ties.  I need some "good enough" on hand, but I also to pay-up and kick things off sometimes with a "use one and be done/ treat myself"  varietal by going up another $ 20 or so a bottle.  So far that's landed me on 2 faves in that category  >  _Angel's Envy_  and  _Eagle's Rare_. ..both names I had only read about but wasn't able to secure easily in Ontario.  They both are "port finished" and I find them smooth as all hell and an excellent first pour.  Then I will throttle back to one of my others, and by then I am not really that discriminate amongst them any longer.  Probably I would say that I prefer _Jim Beam Double Black_ (by far the best value of the bunch IMO) or _Legent_ the most from that photo grouping but it is a pretty close race still and I wouldn't say no to any of them.

After having this personal revelation, I've done more reading since the selection of bourbons over the border in their spirits depots are vast and almost overwhelming.  I have ID'd a few others to try in that same ore-vein once I finish off some of what I have on hand now...

I_saac Bowman Port Finish_, _Redwood Empire _ and _Starlight  by Carl T. Huber’s _are all new names on my watchlist from that research of port finished bourbons unless I find their price-points are beyond my pay-grade.   But I have no idea how hard they will be to find or if they are even in my affordability wheelhouse.  So that is where I am in this rabbit-hole journey.  If I end up landing on _Angel's Envy _and _Eagle's Rare _from an affordability perspective and representing the "good stuff", back-filled with just about any of the "also rans" at about $ 20/bottle less, then there will be worse travails in life for my remaining days. 

Good luck with you Sir on your own personal quest for whisky/whiskey self-fulfillment.  Hopefully we can raise a glass together someday in a shop surrounded by chip-making machine (which should likely remain idle thereafter).


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## thestelster (Feb 6, 2022)

PeterT said:


> I'd like to see your bead blasting & blue-ing when the opportunity arises, please & thanks.
> What about heat treating, do you have your own shop facilities?


Hi Peter, my bead blasting cabinet is a Cyclone 42"x24" which I bought from KBC long time ago.  I've only had to replace the gloves once, and the glass viewing plate, which I accidentally broke.  I replaced it with a lexan sheet.  For media, I use glass beads which gives a very nice soft matte finish.  But you still have to sand down your parts before bead blasting.  It will not remove machine marks.  

I only rust blue now.  Thats my sweat box.  Small hot plate at the bottom that I put distilled water into to create the humidity.  I've got a set of shotgun barrels in there now which I blue a little while ago, and getting everything else prepped.  Hot water boil tank is in the shed in the back yard fuelled by propane.  Another tank of oil which I heat up and put the finished parts into.  Carding is done with a fine wire wheel powered by a DC motor which I can control the speed.


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## Chip Maker (Feb 6, 2022)

I too like both bourbon and scotch. They both have their merits! The better the swill, the price goes up. Living in Ontario, I'm forced to purchase thru the LCB0. I'm not sure if you're aware of the scotch and bourbon lotteries the LCBO puts on 3-4 times a year for harder to obtain bottles here. If you subscribe to Vintages email list, they will notify you when these lotteries take place. You don't actually win the bottle, you win the option to purchase it. Blantons, Stagg or even Pappy Van Winkle to name a few. Or 25 yr Ardbeg or Highland Creek.

Stuff comes in dribs and drabs to different stores as well and I find looking on the LCBO website weekly pays off. Here's a link to what I would say is a really good bargain for a bourbon. There's usually a limit of two when it does show up!









						W.L. Weller Special Reserve Bourbon | LCBO
					

Wellers is the original bourbon that replaced rye for wheat creating an extremely smooth taste. Shows complex aromas of caramel, oak, sweet corn and butterscotch. This is sweet, creamy and smooth with flavours of toasted nut and vanilla, along with lingering honey and spice tones. Drink this neat, o




					www.lcbo.com


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## thestelster (Feb 6, 2022)

LeakyCanoe said:


> Scotch is just OK to me...it's my wife's choice of whisky, but I always preferred dark rums after getting exposed to those on trips to the Caribbean.  Of the Scotch I've had, I like the nicer _Abelour _the best of all.  The rest I generally find harsh or crazy peaty.  Bourbon is now my new fave.  And I think it is because of the underlying sweetness.
> 
> I really have a hard time pulling a leader out of that grouping I sent.  Those were all LCBO purchases, that being pretty much the extent of my booze shopping universe since the pandemic began.  So Doug Ford won't be happy to hear that with the border beginning to open up that I have been back over into the U.S. again.   _BAM ! _   The selection, even at Duty-Free on the way over when I picked-up a bottle of 4 Roses, offered up considerable new choices in the price notch just up from that grouping.  And we're not talking Pappy Van Winkle or even $ 100+/ bottle stuff.  Apparently all the hipsters have discovered it too, along with me...so the selection is absolutely stunning there.
> 
> ...


Ok, I guess I'm going to make up a shopping list.  And/or a Xmas/birthday want list!!


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## thestelster (Feb 6, 2022)

Well, finished machining flutes on another barrel today.  The rest of the week will be truing the actions and bolts, threading, chambering, crowning, install the muzzle brakes, bead blast and assemble.


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## DPittman (Feb 6, 2022)

thestelster said:


> Well, finished machining flutes on another barrel today.  The rest of the week will be truing the actions and bolts, threading, chambering, crowning, install the muzzle brakes, bead blast and assemble.


Looks nice. I wish I could hang out in your shop all next week.


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## PeterT (Feb 6, 2022)

Very snappy looking.


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