Barrel Advice

[MajorJim]

This is getting frustrating...

Coming down to the wire on my build and it is time for a barrel.  Got the Youong bolt carrier and the bolt itself should be ready in September. 

Went through the whole carbon barrel analysis, and I was set to go that direction.  Two unanswered emails and one answered phone message leter, I am passing on that option.  My view is that if a ready to buy buyer has to go through that for the sale process, what is the service level going to be like? 

Just called White Oak Precision.  Described what I wanted to Paul, and they told me I needed to go through one of their retailers - D9 Firearms or another.  They really did not like to do 1 off type barrels.  If one of their retailers could put a "group buy" together, they could handle the production without messing up their line for one barrel.

Have to say I was a little shocked at the response, based on what I have read on many forums about White Oak's service and flexibility. 

In terms of what I want, this is the wish list:  21" chrome moly barrel (Noveske seems to have hit a sweet spot with their 21" offering, but that is only for the AR10 style receivers, not DPMS style. )

Chamber in .308 Obemeyer, 1:10 twist.  Contour  I can be flexible on - The Noveske looks like it is a heavy #9 target, but I could certainly deal with an AMU/MTU or M24.  I would have the barel fluted, primarily to cut down on weight. 

I have zero interest in making a market for a new barrel for White Oak that competes with the Noveske model. 

I can probably put my hands on a Rock 5R blank, but I'd have to get into someone's queue for the finish and chambering work. 

Krieger is an option, but is up there on both a time and expense scale.

Any suggestions?

Thanks

Jim

[MajorJim]

Just fired this off to Krieger:

Would you be willing to take a crack at this AR 308 (DPMS style) design?

Going from the dimensions you have on your contours page:

A= 1.250

B= 5 (Rock Creek uses that for chamber length)

Gas Block-.937 (your block)

C=.875

D=20

E=21

Fluted chrome moly barrel, 1:10 twist, 5R rifling (I know, I know) .308 Obemeyer chamber

Noveske seems to have found a sweet spot with their 21" barrels (#9 heavy contour).  Rock Creek barrels are highly regarded for their accuracy.

If you can do this, I am ready to commit.

Thanks

Doing some research, the Noveske 21" offering for Armalite receivers is getting some pretty high praise.  I compared Mike Rock's contours with Kriegers, and Rock uses a chamber length of 5"  for its AMU/MTU contours while Krieger uses 2.75".  Something to be said for a longer chamber on the Rock barrels, as I believe many will attest to. 

The overall contour does not exactly match any one, coming closest to the Rock Sendero or the Krieger #9 Heavy Target.  Krieger lists the weight of their heavy target at 6.5 pounds for a 27" barrel. so we are at about .24 pounds an inch.  Making allowance for more weight at the bore, it looks like shortening the barrel to 21" would take the total weight down to a little over 5 pounds.  Fluting whould hopefully shave it down to under 4.5 pounds. 

I'll let you know what I hear. 

[imschur]

Have you spoken to Rainier? How about JP?

Also contact branson1369. He has a good line on barrels

[Jgun]

You say that the Noveske is not an option because it's Armalite pattern vs DPMS. Can you tell me what receiver your building on? It is my understanding that you can use a Noveske barrel on  the DPMS pattern receivers as long as you use a Armalite bolt. I built my Mega .308 carbine which has a DPMS 1.437"-16 thread instead of the Armalite 18 pitch thread  with a Noveske,  Armalite pattern 14.5" Afghan barrel by using the complete Armalite BCG, but you might possibly be able to use just the Armalte bolt with the Young's bolt carrier. If that serves your needs you could give Youngs a call and ask them.

[MajorJim]

Iron Ridge upper and lower.

[Jgun]

So far, in my admittedly limited experience, I have found that the choice of barrel will have a far greater effect on the accuracy and function of your rifle than the bolt carrier group you use. if it were me, I might consider saving the Young's bolt carrier for another build, and go with an Armalite BCG, if you get the word from either Young's, or Iron Ridge, that you cannot use it, along with an Armalite bolt, with the Noveske barrel, for your build. That is, assuming the Noveske 21" barrel meets your needs. I will tell you this, I have used the Noveske stainless barrels (not the 21's) for both AR.308, and AR 15 builds, and recommend them highly.

[Matt.Cross]

You could also talk to Lothar Walther, you might have to wait but they are more than willing to accommodate 1-off custom barrels at an unbeatable price.

[MajorJim]

Found a bit of interesting news,  Bettin Custom posted that they no longer offer ABS barrels.  They note on their site that ABS sold the patent to XPA, Xtreme Precision Armaments, in Montana.  I believe Jense is somehow associated with XPA, if not one in the same.  Same city anyway.   

[MajorJim]

You could also talk to Lothar Walther, you might have to wait but they are more than willing to accommodate 1-off custom barrels at an unbeatable price.

Matt,

I actually have a message into Woody over at LW.  This caught my eye:  http://www.lothar-walther.com/396.php

[MajorJim]

Some interesting information on carbon fiber.  The concept of wrapping carbon around a barrel is sold as a way to get the barrel to cool faster.  In other words, in transferring heat away from the barrel, it is said to act as a heat sink.

When using synthetic material, however, there is also the possibility that the wrap is actually acting as an insulator.  Wrap a barrel with asbestos, and it will feel cool as well.

Steel is a good conductor of heat.  So is aluminum and copper.  Steel will heat slower than aluminum or copper, but will also cool slower. 

Carbon?  Well, it does have insulating properties, depending on the direction of the fiber.  Wrapped the wrong way, a carbon barrel can actually direct heat back to the barrel.

I started thinking of an industry that uses heat sinks and is generally at the forefront of that technology.  The computer industry!  The quote below can be found in the article at the following link:

http://rtcmagazine.com/articles/view/100944

Heat sinks have historically been the PCB workhorse for thermal management. They help keep devices at temperatures below their specified maximum operating temperature. There are many versions, different designs and various ways of optimizing heat sinks. Over time, the technology has progressed with the use of new materials. For example, carbon fiber and boron nitride are recent materials applied to heat sinks. High thermal conductivity fiber spreads heat well at 800 watt per meter Kelvin (W/m-K) in the direction of the fiber. However, at 0.5 W/m-K, it doesn’t spread heat up and down very well.

Developers have applied boron nitride crystals as a way to efficiently move heat from one fiber ply to the next. These crystals are used to “salt” carbon fiber sheets or prepregs. Two or more sheets are then laminated together to form the heat sink material, and throughput for up-down directions has been improved from 0.5 to about 4 W/m-K.

Due to their high cost, however, these materials will likely find limited use in future PCB fabrication and may not replace aluminum heat sinks in many applications. Still, carbon fiber heat sinks may best be used in systems that don’t use air-cooling. These may include aircraft, missile and spacecraft components, automobiles, high-end computers and medical equipment.

Basically the same conclusion here: 

http://www.nexlogic.com/Portals/0/New-Materials-and-Techniques-Tackle-PCB-Thermal-Management.pdf

I have used boron nitrade in bullet coating, and the stuff ain't cheap!

A little beter explanation of just how that technology works here: 

http://www.mdatechnology.net/update.aspx?id=a4103

As with making lasagna, the trick to making improved heat sink carbon fiber is in applying the ingredients in the right places. High thermal conductivity fiber spreads heat very well in the direction of the fiber, but not very well in the transverse directions (up and down). Boron nitride is a hexagonal, flat-plate molecule and forms into crystals. The crystals can carry heat very well from one fiber ply to the next. Salt a thermoset resin carbon fiber sheet (called "prepreg") with boron nitride crystals, layer another prepreg sheet on top of that, repeat the procedure, laminate the whole thing together, and you create a material that is capable of transferring heat down through the sink as well as away towards the edges.

Getting just the right amount of powder into the mix turns out to be another key. Use too little, and it doesn't have enough effect. Use too much, and the laminate tends to fall apart. XC Associates' application mechanism has improved since the early days when researchers applied the powder "using something like a sugar shaker" according to company president John Bootle.

The improved laminate is not a theoretical product. XC Associates is working in partnership with the Applied Physics Laboratory of the Johns Hopkins University to provide a heat sink for a radiator component on a Mars explorer spacecraft. Raytheon Missile Systems was also interested in testing the properties and reliability of a salted composite carbon fiber heat sink as a potential replacement for the heavier beryllium-based heat sink in the LEAP missile program. Raytheon determined that the composite could remove heat as well as a sink made of beryllium, for a third of the cost. Other major aerospace corporations as well have expressed interest in the new material and await its spaceflight qualification.

Because making this improved carbon fiber sheet is expensive, laminates incorporating boron nitride powder crystals may never replace simple aluminum heat sinks for many applications. For machines producing large quantities of heat in confined areas, in which air-cooling is not an option, composite fiber heat sinks may be optimal. A six-inch square card, for example, can handle a heat flux of anywhere from 50 to 75 watts; an aluminum heat sink of equal thickness would only be able to handle a 40-watt flux.

It sounds like the semi conductor industry is going in the carbon direction, but for now, if air cooling is used, aluminum is first choice.

I have no clue what technique the carbon wrapped barrel makers use in their product, but it sounds like it is quite involved and expensive if you are going to use the carbon as a heat sink.  Seems to make sense - if the barrel cools faster, barrel life is prolonged.

But is carbon wrap cooliing via acting as a heat sink or acting as insulation not allowing heat to escape?

Since I don't shoot in an environment where air cooling is not possible, I think I am going to give the Lothar Ultralight with the aluminum alloy sink a closer look.   

[Robocop1051]

Are you aware that JP rifles use heat sinked barrels?

My purpose for a CF barrel wasn't so much for barrel life. I wanted a heavy (or larger) contour barrel that wasn't going to weigh 60% of the rifle. CF is also stiffer than steel. By shortening my barrel to 17" I cut vibration, by making it a .875 contour I cut more vibration, by wrapping it in CF I have taken care of nearly all the vibration possible.

I just wanted a <8# semi auto 308 that shot sub-moa.

[98Z5V]

If the Noveske barrel fits what you want to duplicate, then just get it.  Run an Armalite AR-10 bolt in your current BCG, and it'll be fine.  The bolts will work in any bolt carrier - carrier brand doesn't matter, as long as the bolt itself matches the barrel extension on the barrel you have.

[Jgun]

When I purchased my carbon wrapped barrel, one of the reasons that I chose ABS, was because I was led to believe that the strand orientation and actual chemical composition of their carbon caused it to work as an effective heat sink. It was also explained to me that the manufacturers using the carbon that did not effectively dissipate the barrels heat, had to deal with another problem, that being the fact that the barrel heats up and expands when shooting, while the carbon does not. with the other type of carbon, their was a tendency for the barrel and carbon wrapping to delaminate due to this dissimilar expansion/contraction. I was told that the way the other manufacturers were preventing that was by applying the carbon in such a way that when the barrel was cool the carbon was under longitudinal compression and when the barrel heated up that would be reduced, which was not conducive to best accuracy.

Mike at ABS, told me that their testing had shown almost double the accurate life from the barrel. He went on to say that when/if the barrel was shot out, it could be re chambered for .338 federal and would be good for a second life.

Now all of those claims of barrel tension and insulating properties would be difficult for me to verify through my own testing, but I think that if you remove a substantial amount of steel from your barrel (reducing it's effectiveness as a heat sink) and then wrap it with something that is very effective at insulating (the wrong type/application of carbon) I would expect that insted of extended usefull life, you'd be more likely to have accelerated  wear and dramatically reduced barrel life. I have been led to believe that the military is using these barrels in some applications, if true, I doubt that would be the case if the carbon wrapped barrels were in fact a bad design that would be prone to sooner failure.

For myself, I went for the carbon, for two reasons, one, hoping for a dramatic weight reduction, which I did not find to be the case with my .750" 18" long barrel. Perhaps the weight savings would have been more dramatic on a 24" bull barreled  gun. The other reason I went for it was the desire to experiment an try something that I had never tried before. So far I have found the gun/barrel to be lighter (1.5 lbs lighter than my 14.5" Noveske barreled .308) and it seems to be accurate, but that may be more a result of a custom made Rock Creek barrel than of the carbon wrapping.

I think that if you decided that you wanted to try one , it would be something like ordering a custom made barrel from one of the high end barrel mfgs, along with a certain amount more aggravation due to the fact that thee aren't that many choices on where to go, which means that your likely to have a greater wait, and obviously greater expense. Is it worth it? Only you can decide.

[imschur]

Carbon fiber is a great heat sink as long as the proper fibers are used and its bonded to the surface correctly. That said it would be great if someone published data on the subject. Being a curious guy I would like to know the thermal properties, the temperature curve the barrel goes through and what really has me curious how much carbon fiber is enough to dissipate the heat properly? Does matching the barrels diameter just happen to give you what you need? Is more better? up to what point.

I sure like the idea of these barrels

of course Im drifting off topic here

[MajorJim]

Just an update.

Last night, I sent an email off to XPA:

Subject: Carbon Barrels

Saw that XPA has taken over the ABS carbon barrel business. 

Have you started production and/or have any available for a LR-308?

Thanks

And got a reply from XPA's production manager:

Hello Jim,

Thank you for your interest in our products.

We have started production in Montana. All the barrels are built to suit. What exactly are you looking for and we will make it happen.

I sent him a copy of the substance of the issues raised above with carbon - heat dissapator/sink versus heat insulator - and asked if he could give me some insight on what they do to their barrels to insure the heat moves out of the barrel.  I'll update if they respond.

The good news is that XPA is ready to roll with ABS's methods and patents.  Probably just as  good news is that I heard back from Lothar on their Ultrlight with the aluminum heat sink posted at the link above.  And they will also customize the barrel with their LW-50 match stainless (OAL, chamber length, gas port diameter, barrel diameter before and after the port, threaded muzzle, etc).  So we appear to have two different choices in lightweight heat sinked barrels that should both theoretically improve barrel life and multiple shot accuracy.

Stay tuned. 

[Robocop1051]

Jense Precision / XPA are the ones building my barrel. Mike is very personable and knowledgeable.

[MajorJim]

Any thoughts or experience with Douglas match air gauged barrels? 

 

[imschur]

Any thoughts or experience with Douglas match air gauged barrels? 

Thats the good stuff

[MajorJim]

What do you think of this one:

http://www.shop.superiorbarrels.com/product.sc?productId=118&categoryId=15

Very close to the one I had in my mind.  22" versus 21", contour very close, .308 Match chamber, 1:10 twist, button rifled 6 groove, .875 gas block, and comes in at 4 pounds 4 ounces without fluting.  Douglas Match XX  air gauged

And I really liked this:

http://www.shop.superiorbarrels.com/images/AR10-5.jpg

[imschur]

Im not familiar with their work. Sounds good though

[MajorJim]

Received a response from XPA on the carbon dissipation/insulation questions.  If they told me they'd have to kill me:

Jim,

Much of what you found is accurate. I am not at liberty to talk about the process we use, but not all carbon is created equal and using the correct carbon in the correct recipe works to dissipate heat for us quite well. The heat isn't the only attribute with carbon, it also dampens vibrations, much like the carbon fiber arrow in the archery business. We have seen barrels that exceeded twice their likely lifespan when kept cool from the carbon wrapping process as well.

Greg

[MajorJim]

The response from Krieger:

We don't make an AR-10/DPMS barrel in the contour, material, or 5-R rifling as you requested. We can however refer you to Accuracy Systems. They will purchase a blank from us and turn it into a barrel for the DPMS-LR platform. Contact http://www.accuracysystemsinc.com/index.php for details and pricing on your project.

Thank You,

Krieger Barrels, Inc.

So, after buying a $400 blank frim Krieger, about another $300 plus a wait of ???? to get a barrel (Krieger charges $240 for chambering and headpsacing to your bolt, there there is the coutouring, and if you want fluting, another $125.  Best guess at this point is that would add another $300 plus to the barrel alone.  That makes $900 for a carbon wrapped barrel, or $875 for a Lothar with the aluminum heat sink, not look so bad. 

[imschur]

Model 1 Sales is selling Krieger Match barrels for AR-10. Also note Armalite has a custom shop that provides serious competion barrels. Shoot Uncle Armalite a PM if so inclined.

[MajorJim]

Thanks but I have a DPMS style receiver.  Still, I took a look - $620 for the National Match Barrel in CM(I assume it is already contoured and chambered), and another $75 if you want muzzle threads.  The stainless version will run you another $200.  And BYOB (Bring Your Own Bolt).  Without any finish (bead blasting or melonite), and without fluting. 

Stainless with threaded muzzle will run you $895 for the barrel alone.  Prices quoted by Lothar Walther on their LM-50 with the Aluminum shroud (heat sink) was $875, and a carbon wrapped Rock barrel from XPA/ABS at $900. 

The Douglas came with a matched DPMS bolt, and right about now that is looking like a pretty good deal. 

[98Z5V]

Thanks but I have a DPMS style receiver. 

That doesn't matter not a bit, as I previously stated.  Doesn't matter what type of receiver you have - the barrel extension will fit into that receiver like it was made for it. 

All you need to do, and make sure you do, if you wish to run an Armalite-design barrel in your DPMS-style upper receiver is make sure you use an Armalite bolt.  Even if you have a DPMS bolt carrier, the Armalite bolt will fit it.

The bolt has to match the barrel extension.  As long as those two parts are style-specific, it doen't matter which brand of receiver you mate them to - they'll go right into DPMS or Armalite.  The opposite is true, also - DPMS barrels (and their compatible bolts) will go right into an Armalite receiver, the the DPMS bolt will go right into an Armalite bolt carrier.

Trying to help you here, man, but I don't think you can smell what I'm spreadin'.