Trying to get my learn on, specifically for a semiauto AR pattern .308 or 6.5CM rifle. BUT also interested in info pertaining to bolt guns.

Fluted vs non fluted barrels? What mission drives that decision train, or do they not make much of a difference? 

What I *think* I know: 

Fluted can be lighter weight for the same length and style barrel. 

Fluted will heat up faster than a standard barrel of the same outside diameter. Fluted will also cool faster than a standard barrel of the same outside diameter (due to the thinner metal? Or the increased surface area like radiator fins to shed heat). 

Standard is stiffer than fluted given the same length and outside diameter .

 

SCHOOL me, debunk or confirm what I think I know? What's the decision making process for this interesting barrel feature? 

 

 

 

 

Joined:      14 January 2010                Location:  MAINE

Original Post

I think most of your “I think I know” is correct.  The only thing is that they heat up faster.  Not sure about that.  But if I put my logical hat on and think about it, it does make sense to me.  

The decision to go that route is not something I’ve ever considered.  So I’m no help there.  For my needs whatever benefit a fluted barrel offers is probably of minuscule value to me.  

Mojo/Mark
__________________________
Yo homey, is that my briefcase...?
Vincent from "Collateral"
__________________________
You want the good life, you break your back, you snap your fingers, you snap your neck... Prong/Demon Hunter
__________________________

That's one... 


Joined: 9/30/09
Location: Northern Nevada (Reno/Sparks)

He's correct, a fluted barrel of the same outside diameter as an unfluted barrel will heat faster because it has less mass, i.e. a less heat sink.  And it cools faster because of the increased surface area.  I don't like the looks as much () on a spiral fluted barrel, but they are supposed to eliminate potential weak spots in the barrel caused by a long, thin spot parallel to the bore when the flutes are longitudinal.  It probably isn't much of an issue unless you have a cheap barrel trying to justify expensive, or the fluting goes too far.  I haven't heard any noticeably frequent occurrence of barrels splitting at the flutes.  I have a couple of BCM fluted barrels (weight reduction) and I haven't had any issues.  Then again, I haven't been running the trigger fast enough to cause a lot of heating or stress.

I don't know how valuable the fluting is for cooling.  Radial cooling fins were common for machine guns until they weren't.  That may have been because they weren't very effective, or simply that the cooling benefit was outweighed by the extra cost. 

-------------------------

Mark

Swear allegiance to the flag Whatever flag they offer

Never hint at what you really feel

Teach the children quietly For some day sons and daughters

Will rise up and fight while we stood still

 

Joined:  2/24/2003                          Location:  Nevada, USA

We fluted DMR, SR-25, and AR-10 barrels to drop maybe a quarter to half a pound.  It adds a little cost, not so much if you have the CNC organic to your shop.

Nothing like hauling around a heavy bar to get make you want a lighter one for nearly the same performance. 

I am not and have never been someone who demanded a longer, heavier weapon to do my job.

Roger on all points. I assumed there was a reason we weren't seeing ribbed style heat vanes on modern barrels (to my knowledge) but wasn't sure if that was due to fluting. 

Continuing the learning engagement, and getting into the weeds/minutea of things, spiral vs straight fluting it sounds like and stands to reason that spiral may be preferable? 

Cost is a great point also, these extra machining steps aren't free. 

 

Thanks for the talk! 

 

 

 

 

 

Joined:      14 January 2010                Location:  MAINE

Preferable.  I don't know.  The theory of the spiral fluting superiority may be correct, but.  Is it a theoretical or practical superiority.  Let's say you can remove more weight for the same strength and you barrel is 4 oz lighter.  At a 50% cost increase for the barrel.  Is the cost worth the benefit?  LWRCi uses spiral flutes on their barrels.  You might want to contact them and see what they say about the benefits and/or superiority of spiral vs. longitudinal.

-------------------------

Mark

Swear allegiance to the flag Whatever flag they offer

Never hint at what you really feel

Teach the children quietly For some day sons and daughters

Will rise up and fight while we stood still

 

Joined:  2/24/2003                          Location:  Nevada, USA

LobsterClaw207 posted:

Roger on all points. I assumed there was a reason we weren't seeing ribbed style heat vanes on modern barrels (to my knowledge) but wasn't sure if that was due to fluting.

 

Could it also be that those "heat vanes" were negated by quick change barrel systems?  I'm thinking machineguns vs rifles though, such as a ZB26 or Hotchkiss 1914.  Could be also why the water-cooled MG's of WW1 faded away too?

"These are the rules. Everybody fights, nobody quits. If you don't do your job I'll kill you myself."

 

Joined: 04/01/2004     Location:  Twin Cities, MN

The only significant drawback to water cooled MGs is mobility.  The fact is, they worked extremely well.  The rates of fire achieved by water cooled MGs during WWI could not have been achieved with quick change barrels.  However, warfare has changed since then and we don't shoot a million rounds from fixed positions any longer.   

-------------------------

Mark

Swear allegiance to the flag Whatever flag they offer

Never hint at what you really feel

Teach the children quietly For some day sons and daughters

Will rise up and fight while we stood still

 

Joined:  2/24/2003                          Location:  Nevada, USA

Dorsai posted:

The only significant drawback to water cooled MGs is mobility.  The fact is, they worked extremely well.  The rates of fire achieved by water cooled MGs during WWI could not have been achieved with quick change barrels.  However, warfare has changed since then and we don't shoot a million rounds from fixed positions any longer.   

I don't really agree with that last sentence.  Remote outposts in Iraq and Afghanistan have both been largely static and attacked enough that improved machine gun coverage would help.

In a peer-adversary conflict, yes I think you'd be correct.  Even in eastern Ukraine with the re-emergence of trench warfare, they need to be mobile enough to un-ass an area quickly.  Russian fires are devastating.

---------------------------------------------------

Regarding barrel fluting, AMU did it on the M16A4 SDM rifles they made for 3rd ID.  I'm not entirely sure of their specific reasoning, but I personally appreciated the weight savings.  I'll take any weight savings I can in combat if they don't have too much associated cost (not necessarily money).

---------------------------------------------------

Pappy posted:
Dorsai posted:

The only significant drawback to water cooled MGs is mobility.  The fact is, they worked extremely well.  The rates of fire achieved by water cooled MGs during WWI could not have been achieved with quick change barrels.  However, warfare has changed since then and we don't shoot a million rounds from fixed positions any longer.   

I don't really agree with that last sentence.  Remote outposts in Iraq and Afghanistan have both been largely static and attacked enough that improved machine gun coverage would help.

In a peer-adversary conflict, yes I think you'd be correct.  Even in eastern Ukraine with the re-emergence of trench warfare, they need to be mobile enough to un-ass an area quickly.  Russian fires are devastating.

I thought about that, but decided the cost of producing a limited number of water cooled guns for specialist type applications was probably excessive.

-------------------------

Mark

Swear allegiance to the flag Whatever flag they offer

Never hint at what you really feel

Teach the children quietly For some day sons and daughters

Will rise up and fight while we stood still

 

Joined:  2/24/2003                          Location:  Nevada, USA

Pappy posted:

Regarding barrel fluting, AMU did it on the M16A4 SDM rifles they made for 3rd ID.  I'm not entirely sure of their specific reasoning, but I personally appreciated the weight savings.  I'll take any weight savings I can in combat if they don't have too much associated cost (not necessarily money).

It was to try and drop the weight to a little less than a Colt HBAR with the DD M4 rail. 

Not much, but we figured it would offset the added weight of the bipod.

The rail itself actually weighs less than standard fore-ends with the heat shields.

Image result for usamu fluted m16 barrel

Dorsai posted:

...I don't know how valuable the fluting is for cooling.  Radial cooling fins were common for machine guns until they weren't.  That may have been because they weren't very effective, or simply that the cooling benefit was outweighed by the extra cost. 

Some time back I saw 2-3 references from arms boards doing testing along these lines as a way to reduce wartime costs. Think of how the Thompson evolved to be a much, much simpler gun. With: basically the same effectiveness. 

The fluting usually works (some, not so much, but usually) but... enough? These reports I saw showed that it wasn't enough to matter practically. Other systems the same way, like finned aluminum cooling sleeves pressed over the barrel, which do work great on machines, electrical components, etc. I think some of the effective-value thing is that a gun works just fine over a fairly wide range of temperatures, which much other stuff does not. 

(Related: the .308 conversion of the BREN did one barrel per gun. It's effectively an AR; mag fed guns can't fire fast enough to burn up a barrel, but they didn't notice for a few decades.)

In the cases of those guns that dropped cooling fins, many times the final barrel profile dropped the cooling fins entirely, so the barrel weight dropped as well. 

 

As far as water cooled MGs today, we still have change barrel guns. It would seem plausible to make a few hundred (or a few thousand) water cooled barrels. You clip them on as needed, but don't permanently modify the gun.

I wonder if we could do something even snazzier that just open cycle water cooling. Pressurized systems with radiators instead? Ethylene glycol? Nitrate salt? Would be fun to see what could be come up with. 

The things that will destroy America are prosperity at any price, peace at any price, safety first instead of duty first, the love of soft living and the get rich quick theory of life. – Theodore Roosevelt

 

Joined: 19NOV2004   Location: Mission, Kansas

shoobe01 posted:
Dorsai posted:

...I don't know how valuable the fluting is for cooling.  Radial cooling fins were common for machine guns until they weren't.  That may have been because they weren't very effective, or simply that the cooling benefit was outweighed by the extra cost. 

 These reports I saw showed that it wasn't enough to matter practically. Other systems the same way, like finned aluminum cooling sleeves pressed over the barrel,

Lewis gun. The whole Al flutes & tube were apparently ineffective.

(Related: the .308 conversion of the BREN did one barrel per gun. It's effectively an AR; mag fed guns can't fire fast enough to burn up a barrel, but they didn't notice for a few decades.)

Ahem.  Want to see a L4A4 spare barrel bag?

As far as water cooled MGs today, we still have change barrel guns. It would seem plausible to make a few hundred (or a few thousand) water cooled barrels. You clip them on as needed, but don't permanently modify the gun.

Tried that with a M60...doing the jacket around the gas system was a bitch.  Given the projected mass of the barrel/jacket/coolant combo I decided I'd rather have another spare barrel.  If you look at a Commonwealth SFMG operation...you will see 2-4 MAG58/L7A2 barrels sitting next to the tripod- often on improvised racks (star pickets) to aid cooling down.

I wonder if we could do something even snazzier that just open cycle water cooling. Pressurized systems with radiators instead? Ethylene glycol? Nitrate salt? Would be fun to see what could be come up with. 

French had a HMG design that squirted a mist of water up the barrel between shots.  Now, what if you had a system that could flush the barrel or gas system out with say...freon?

Cheers

I think pressurized systems could be doable. There are water/liquid cooled motorcycles.  Aren’t BMW’s liquid cooled? If it can be done on a motorcycle engine probably no resson it couldn’t be miniaturized to fit an MG. 

Mojo/Mark
__________________________
Yo homey, is that my briefcase...?
Vincent from "Collateral"
__________________________
You want the good life, you break your back, you snap your fingers, you snap your neck... Prong/Demon Hunter
__________________________

That's one... 


Joined: 9/30/09
Location: Northern Nevada (Reno/Sparks)

Miniaturization? They have water cooled consumer computers! 

We could do it. IF, it was worth it, and reliable enough. Needs to be better than barrel changing in every way. Would be cool for someone to get built and try it out. So, get on it already

The things that will destroy America are prosperity at any price, peace at any price, safety first instead of duty first, the love of soft living and the get rich quick theory of life. – Theodore Roosevelt

 

Joined: 19NOV2004   Location: Mission, Kansas

Linz posted:
shoobe01 posted:
Dorsai posted:

...

...

(Related: the .308 conversion of the BREN did one barrel per gun. It's effectively an AR; mag fed guns can't fire fast enough to burn up a barrel, but they didn't notice for a few decades.)

Ahem.  Want to see a L4A4 spare barrel bag?

Yup. News to me. Common or just a few insisted they wanted spare barrels anyway? 

 

Linz posted:
shoobe01 posted:
Dorsai posted:

...

As far as water cooled MGs today, we still have change barrel guns. It would seem plausible to make a few hundred (or a few thousand) water cooled barrels. You clip them on as needed, but don't permanently modify the gun.

Tried that with a M60...doing the jacket around the gas system was a bitch.  Given the projected mass of the barrel/jacket/coolant combo I decided I'd rather have another spare barrel.  If you look at a Commonwealth SFMG operation...you will see 2-4 MAG58/L7A2 barrels sitting next to the tripod- often on improvised racks (star pickets) to aid cooling down.

Part of why I was thinking of not an old school open cycle evap cooling system, but you do something like have a wide but short cooling box, and fins machined/attached to the side of the barrel for minimal other changes. 

The things that will destroy America are prosperity at any price, peace at any price, safety first instead of duty first, the love of soft living and the get rich quick theory of life. – Theodore Roosevelt

 

Joined: 19NOV2004   Location: Mission, Kansas

I don't think you want something like freon that cools the barrel rapidly.  Uneven cooling over it's length would probably warp it, maybe even cause it to crack.  The big advantage of the water cooled barrel, if you have a water supply, is that the barrel never gets really hot.  It is constantly cooled and as long as you can exhaust steam and supply water, the barrel really can't get much hotter than 211deg.  Enough barrels to keep changing them out as they get hot, and sticking to barrel changes at the proper intervals, would also suffice, but being able to keep up a constant rate of fire while attaching fresh belts to the end of the one being shot could make a difference.   But think of the context?  Water cooled Maxim guns were first used in colonial battles when waves of men were coming at outnumbered, stationary forces.  Men in trenches, or behind barricades, in squares, etc.  Then WW1 in the trenches with mass infantry attacks. 

-------------------------

Mark

Swear allegiance to the flag Whatever flag they offer

Never hint at what you really feel

Teach the children quietly For some day sons and daughters

Will rise up and fight while we stood still

 

Joined:  2/24/2003                          Location:  Nevada, USA

shoobe01 posted:

Miniaturization? They have water cooled consumer computers! 

We could do it. IF, it was worth it, and reliable enough. Needs to be better than barrel changing in every way. Would be cool for someone to get built and try it out. So, get on it already

If’n I only had the resources, I may have the technical skill/knowledge but not the financial backing to even consider launching such a project.  I’ll never be a millionaire. 

Aint no fun, no it ain’t no fun, waiting ‘round to be a millionaire.  Ronald Scott (aka Bon Scott, AC/DC), cue bagpipes. 

Mojo/Mark
__________________________
Yo homey, is that my briefcase...?
Vincent from "Collateral"
__________________________
You want the good life, you break your back, you snap your fingers, you snap your neck... Prong/Demon Hunter
__________________________

That's one... 


Joined: 9/30/09
Location: Northern Nevada (Reno/Sparks)

Dorsai posted:

I don't think you want something like freon that cools the barrel rapidly.  Uneven cooling over it's length would probably warp it, maybe even cause it to crack.  The big advantage of the water cooled barrel, if you have a water supply, is that the barrel never gets really hot.  It is constantly cooled and as long as you can exhaust steam and supply water, the barrel really can't get much hotter than 211deg.  Enough barrels to keep changing them out as they get hot, and sticking to barrel changes at the proper intervals, would also suffice, but being able to keep up a constant rate of fire while attaching fresh belts to the end of the one being shot could make a difference.   But think of the context?  Water cooled Maxim guns were first used in colonial battles when waves of men were coming at outnumbered, stationary forces.  Men in trenches, or behind barricades, in squares, etc.  Then WW1 in the trenches with mass infantry attacks. 

As I recall, many of the Gatling guns came from the factory with felt pads between the barrels.

Idea was crew would soak the pads with water to aid keeping the barrels cool.

shoobe01 posted:
Linz posted:
shoobe01 posted:
Dorsai posted:

...

...

(Related: the .308 conversion of the BREN did one barrel per gun. It's effectively an AR; mag fed guns can't fire fast enough to burn up a barrel, but they didn't notice for a few decades.)

Ahem.  Want to see a L4A4 spare barrel bag?

Yup. News to me. Common or just a few insisted they wanted spare barrels anyway? 

Doctrine.

Some of the L4 series were issued with a single barrel, others with two.

Attachments

Photos (2)

Add Reply

Post
Copyright Lightfighter Tactical Forum 2002-2019
×
×
×
×
×