Turning Material Off of a Heavy Barrel

[mmattockx]

I have an extra heavy AR barrel that I thought was what I wanted, but has turned out to be too heavy for my uses. It is a Shilen match barrel and shoots pretty well for me, but it would be nice if I could take some weight off. Has anyone turned a barrel to knock some weight off? Any effects on accuracy or any other performance metric? Any tips on how to go about removing the weight?


Thanks,
Mark

 

[I Dont Care About You]

Has anyone turned a barrel to knock some weight off?

Yes.

Any effects on accuracy or any other performance metric?

Don't know, I never shot the barrel prior to it being profiled. I'd doubt there were be any serious accuracy problems unless you really thin the thing out. There are lots of pencil barrels or military profile barrels (thin at the back end, thick near the muzzle) that shoot decently well. I think the most important thing would be to not thin out the muzzle area too much.

Any tips on how to go about removing the weight?

I'd suggest a lathe, but you are welcome to try a hand file.

 

[SigWig]

• I-Fluting is probably the best
  

avoid pineapple pattern

I can't figure this pattern out. It doesn't shave much weight and reduces strength

 

[Thunderhog]

I have an extra heavy AR barrel that I thought was what I wanted, but has turned out to be too heavy for my uses. It is a Shilen match barrel and shoots pretty well for me, but it would be nice if I could take some weight off. Has anyone turned a barrel to knock some weight off? Any effects on accuracy or any other performance metric? Any tips on how to go about removing the weight?


Thanks,
Mark

If you ask any gunsmith, the majority will tell you not to turn down a heavy barrel. It can change the harmonics of the barrel and it may no longer shoot very well.

Barrel fluting is an option, but again this also can change the same harmonics.......

I would seek advise from a experienced gunsmith who knows the outcome of these methods that have been tried by others.

May be cheaper to buy the barrel contour you are looking for and sell off the heavy one......

 

[I Dont Care About You]

Yeah, that's fantastic, if you happen to have a $50,000 CNC milling machine with a live 4th axis. Weirdly most people don't.

 

[I Dont Care About You]

If you ask any gunsmith, the majority will tell you not to turn down a heavy barrel. It can change the harmonics of the barrel and it may no longer shoot very well.

One might note that profiling a barrel will change the harmonics of the original blank. At what point is a barrel "finished" and how does one know when a barrel is "finished" such that the harmonics are "correct?" How does the barrel maker know what profile produces the best harmonics when the length can change during the chambering / fitting process?

How do we know that re-profiling a barrel won't improve the harmonics and make the barrel shoot better?

 

[Thunderhog]

One might note that profiling a barrel will change the harmonics of the original blank. At what point is a barrel "finished" and how does one know when a barrel is "finished" such that the harmonics are "correct?" How does the barrel maker know what profile produces the best harmonics when the length can change during the chambering / fitting process?

How do we know that re-profiling a barrel won't improve the harmonics and make the barrel shoot better?

I'm not a gunsmith, only an armorer and a firearms enthusiast.

I stated what my gunsmith and several other gunsmiths have told me. So I cannot answer your questions, sorry.....

Are you a certified and registered gunsmith?

 

[I Dont Care About You]

Are you a certified and registered gunsmith?

There is no such thing in Canada. There is no gunsmithing certification body in Canada and there is nobody to register as a gunsmith with. One can get a Firearms Business License but there is no certification required so anyone can do that with no knowledge or experience in gunsmithing.

I build custom rifles and barrels. I have profiled many custom AR barrels.

 

[Silverado]

How married to the bbl or married to the attempt are you? You could anneal, turn and heat treat, see if it shoots OK? Or farm out the hot work?

 

[Thunderhog]

There is no such thing in Canada. There is no gunsmithing certification body in Canada and there is nobody to register as a gunsmith with. One can get a Firearms Business License but there is no certification required so anyone can do that with no knowledge or experience in gunsmithing.

I build custom rifles and barrels. I have profiled many custom AR barrels.

Well that’s very interesting, the gunsmith in Creston, BC I use is in fact a certified, licensed and registered gunsmith. His name is Josh Salzmann and runs Accurate Rifle Company.
I would be happy to give you his contact information if you would like to tell him yourself of your doubts you have in his certification and credentials.
It’s odd I have never heard of you, other than your moniker, (I don’t care about you).

 

[fiftycalforsquirrels]

A straight heavy barrel is the best for a target barrel. Cooling and stiffness.

Spiral it for weight reduction. Maintains some of the heavy profile but you lose out on maximum stiffness and cooling.

Pencil/sporter barrel for maximum weight reduction. Lose out on all stiffness and cooling benefits to be had.

Harmonics can be worked out in the load and the stock. You cant add stiffness and cooling propertys to a barrel. And what I mean by stiffness, is overall ability to not be affected by harmonics. And what I mean by cooling, is as a barrel heats up, the barrel shifts. So... a fat heavy barrel is as good as it can get, anything else is a downgrade?

disclaimer... I have zero practical experience, that is just what I consider to be accurate as far as my learned theory goes.

 

[FatCatsDad]

Yeah, that's fantastic, if you happen to have a $50,000 CNC milling machine with a live 4th axis. Weirdly most people don't.

I've had good luck using a local machine shop for getting things done.

The guys actually seem to enjoy a change from making pump shafts etc.

It's usually cheap.
Last project was a shotgun barrel I had ported, $100 cash.

I showed him a picture of what I wanted , ran some errands and picked it up 3 hrs later.

 

[struff55]

the buzz word in the rifle world harmonics
i have turned down a few bbl.s om my lathe it actually has a taper attachment so is fairly easy to do but it is a slow process
on a cnc machine where you set it up and walk away for a couple of hours would be the way to go

 

[Jonnyofalltrades]

Barrel profiling is nasty work. Very time intensive unless you have the correct tooling.
I have done it several times, and it always ended up taking 5 times as long as I thought it would.
The details that matter are:
How long is the barrel section that you want to turn down? Longer equals pain.
And,
How much do you want to reduce it? Skinny equals pain.
And,
How picky are you about surface finish afterwards? Shiney equals pain.
Sorry for all the pain, but that's generally what reprofiling is, a pain!

Having said that, I have every intention of turning down more barrels in the future, so I must be a masochist. Practice does make it a little easier.
Being as your barrel is a Shilen, it should be very well stress-relieved. Profiling shouldn't bother it much.

 

[wildphil24]

A straight heavy barrel is the best for a target barrel. Cooling and stiffness.

Spiral it for weight reduction. ...

Spiral is nice but would it be superior to straight fluting?

You cant add stiffness and cooling propertys to a barrel. ... And what I mean by cooling, is as a barrel heats up, the barrel shifts. So... a fat heavy barrel is as good as it can get, anything else is a downgrade?

disclaimer... I have zero practical experience, that is just what I consider to be accurate as far as my learned theory goes.

I'm no expert or physicist either, we're just discussing fluting theory for fun.

I would argue you are wrong about the cooling properties. There's a formula to calculate cooling and the surface exposed to air is an important factor to it. By fluting a barrel you increase that surface, thereby accelerating cooling.

The quality of a heavy barrel is that it takes more shots to warm-up it's extra mass.

For example, let's suppose any barrel was to suffer an important accuracy decline at 80°c. A light barrel may reach that temperature after a string of 20 shots while it'd take 40 shots for the barrel twice heavier.
The fluted barrel with a mass in-between may shoot a 30 round string to reach the 80°c but will cool faster than the 2 others.

Now that assumed those string were shot at rate of fire too fast to allow any meaningful cooling.
There's a slower rate that would allow both the fluted barrel and the heavy barrel to shoot around 50 rounds before they reach the temperature threshold.
There's an even slower rate that would allow the fluted barrel to never overheat while the heavy barrel overheat after 100 rounds.
Slower the rate, more important becomes the other variables like the loads, temperature, wind, sun, etc.

To some extent, fluting also brings a structural advantage. A 10kg h-beam being stiffer than a 10kg rod of the same length and steel. So a 1kg fluted barrel will be stiffer than a 1kg straight barrel of the same material and lenght.
Assuming it's a smart design and not the fancy pineapple previously mentionned.

 

[fiftycalforsquirrels]

Turning it down is real fast if you know your machine. Getting on center is the challenging part. How much off center is acceptable is the question of the day.

 

[wildphil24]

Barrel profiling is nasty work. Very time intensive unless you have the correct tooling.
I have done it several times, and it always ended up taking 5 times as long as I thought it would.
...
Having said that, I have every intention of turning down more barrels in the future, so I must be a masochist. Practice does make it a little easier.
Being as your barrel is a Shilen, it should be very well stress-relieved. Profiling shouldn't bother it much.

Unfortunately, most gunsmith will decline a fluting job just like a reprofiling job. Typically stating the possibility to induce stress/temperature that mess the harmonics. Sometime stating the juice is not worth the squeeze.

You could make it a specialty and work from home.

 

[EDX2308]

Lots of opinions on how to make a barrel lighter.... not one has mentioned "cutting the barrel shorter". Accuracy is maintained but the range is a bit shorter....

 

[fiftycalforsquirrels]

Spiral is nice but would it be superior to straight fluting?

I'm no expert or physicist either, we're just discussing fluting theory for fun.

I would argue you are wrong about the cooling properties. There's a formula to calculate cooling and the surface exposed to air is an important factor to it. By fluting a barrel you increase that surface, thereby accelerating cooling.

The quality of a heavy barrel is that it takes more shots to warm-up it's extra mass.

For example, let's suppose any barrel was to suffer an important accuracy decline at 80°c. A light barrel may reach that temperature after a string of 20 shots while it'd take 40 shots for the barrel twice heavier.
The fluted barrel with a mass in-between may shoot a 30 round string to reach the 80°c but will cool faster than the 2 others.

Now that assumed those string were shot at rate of fire too fast to allow any meaningful cooling.
There's a slower rate that would allow both the fluted barrel and the heavy barrel to shoot around 50 rounds before they reach the temperature threshold.
There's an even slower rate that would allow the fluted barrel to never overheat while the heavy barrel overheat after 100 rounds.
Slower the rate, more important becomes the other variables like the loads, temperature, wind, sun, etc.

To some extent, fluting also brings a structural advantage. A 10kg h-beam being stiffer than a 10kg rod of the same length and steel. So a 1kg fluted barrel will be stiffer than a 1kg straight barrel of the same material and lenght.
Assuming it's a smart design and not the fancy pineapple previously mentionned.

You bring up valid consideration. Which revolves around the objectice of what the barrel is required to do. What if we consider, even though the temperature threshold is reached at a rate of fire such that the straight and fluted is reached in 50 rounds, but rate of fire maintains for another 30 shots. Which one holds or consistently puts them closer to point of aim?

I would say if you took a 30" straight barrel, and took a 30" barrel and fluted it, the straight barrel is more rigid and will shoot more before accuracy decline.

If you were trying to meet a weight restriction but also achieve X barrel length, its hard to say whats better.... 30" fluted at X weight vs 30" straight at X weight.

Or remove the length requirement. 30" fluted, vs 25" straight, weight is equal.

Or, remove the weight requirement and go 30" straight vs 30" fluted.

Edit: if you remove the weight requirement, I'm showing up with a minimum 1.250" straight 30" barrel. So you make a 1.5" fluted 30".....I would show up with a 1.5" straight.

If a guy with a fluted barrel puts a shot clock on a string, the straight always keeps up and may even have an edge.

If a guy with a straight puts a shot clock on it, the flute falls behind.

And I do reckon the rate of fire would have to be extremely slow in order for a fluted barrel to out cool/out shoot a straight barrel. OR, rate of fire is a 5 round group then full cooldown. At that point, the propertys dont mean anything because either barrel never came close to a heat related accuracy decline.

And just incase we forgot... still in full theory mode here.

 

[wildphil24]

Lots of opinions on how to make a barrel lighter.... not one has mentioned "cutting the barrel shorter". Accuracy is maintained but the range is a bit shorter....

Certainly the most simple/cheap option when legally available.