Thread: carbon fiber vs steel

Hey guys and girls just a question that's been bugging me for a while. We all know that a carbon fiber barrel of the same weight is stiffer than steel , well so all iv'e read and been told says so. What no one seems to know or I can't fine is when does carbon fiber equal steel? Say something like a barrel with a fairly standard profile of say 16mm at the muzzle and heading towards 30mm at the action. What diameter would a carbon barrel need to be to equal the stiffness? I see on christien arms site for example their carbon fiber barrels for a blaser is 22mm at the muzzle apposed to 17mm steel. Just wondered if there was a rule of thumb , say multiply x25% to get a close equivalent or something along those lines?

Originally Posted by r87mm

Hey guys and girls just a question that's been bugging me for a while. We all know that a carbon fiber barrel of the same weight is stiffer than steel , well so all iv'e read and been told says so. What no one seems to know or I can't fine is when does carbon fiber equal steel? Say something like a barrel with a fairly standard profile of say 16mm at the muzzle and heading towards 30mm at the action. What diameter would a carbon barrel need to be to equal the stiffness? I see on christien arms site for example their carbon fiber barrels for a blaser is 22mm at the muzzle apposed to 17mm steel. Just wondered if there was a rule of thumb , say multiply x25% to get a close equivalent or something along those lines?

Be careful with weights quoted, a client was quoted 700 grams for an 18" locally produced carbon fibre barrel which was exactly what he was after for his light weight build.

The problem was it was 1100 grams when it showed up, which isn't even close, especially considering I have an 18" fluted SS barrel here chambered the same which is lighter & cheaper ....

The longer the barrel is the more the weight savings are for Carbon VS Steel, some say Steel is still stiffer....

The quality of the internal machining & finish of the barrel is more important that the weight.

Not all carbon barrels are equal, the Proof Research seem to easily be the pick of the bunch so far.

From another forum:

"I have fitted alot of carbon fiber barrels to custom rifles and have learned a few FACTS from my actual hands on testing. This is what I know:

If you take two barrels, for example, two #4 contour barrels, one carbon wrapped, one all steel, the all steel barrel will be dramatically stiffer. Also, the weight reduction on the wrapped barrel will not be much at all.

If you take two barrels, for example, 1.200" straight cylinder barrels,one carbon wrapped, one all steel, the all steel barrel will STILL be stiffer then the carbon wrapped barrel but in the comparision between these two large diameter barrels, the carbon wrapped barrel WILL BE much lighter in this application.

I know this because have taken barrels, chucked them up in the lathe by the shank just as they would be supported by the receiver, then hung 10 lb weights off the muzzle end and measured the flex in the barrels for comparision. In every case, all steel barrels had less flex then the carbon wrapped barrels.

Its true that carbon is stiffer then steel for a given WEIGHT. That is what gets left out of the advertisments. Let me explain further. If you take two rods that are 30" in lenght, both weighing 5 lbs. One all steel, the other all carbon fiber. The carbon fiber rod will be several TIMES larger in diameter then the all steel barrel and yes it will be slightly stiffer as well. Unfortunately, its not practical to wrap that amount of carbon fiber around a barrel sleeve. As such, the strength increase advertisment is simply FALSE in a rifle barrel application.

Now onto barrel weight.

AS mentioned, if your comparing two rifles with large contour barrels, the carbon fiber barrels will be DRAMATICALLY lighter but their barrels will not be stiffer.

IF your comparing sporterweight barrel contours, You can build an all steel barreled rifle that is only marginally heavier then any carbon fiber barreled rifle so application is critical to get the advantage out of these barrels.

Now lets talk about barrel life.

Yes its been proven that carbon fiber barrels cool faster then all steel barrels. It has also been proven that the barrel sleeves used in carbon fiber barrels also heat up faster!!!! So its a bit of give and take here. I would say for a high volumne varmint rifle you could see some benefit in barrel life but in my testing, even with large capacity, hyper performance long range rifles, the barrel life advantage is less then 15%.

Considering that a good quality carbon fiber barrel will cost easily twice what an all steel barrel will cost, in my opinion, its not worth it, especially for a big game rifle that will be fired much more deliberately with low volume shooting.

I have tested a couple ABS carbon wrapped barrels in my 338 Allen Magnum and put them through some torture tests along with two all steel barrels, one from Lilja and one from Krieger. The ABS barrels both used Rock barrel sleeves. The test was to fire five, 10 shot strings. Shooting was done by shooting 10 shots as fast as possible. Let the barrel cool to the point I could just hold my hand on the barrel, repeat with 10 more rapid fire shots and continue to repeat until 50 rounds were down the barrel.

I did this with all four barrels, two ABS, one Lilja, one Krieger. After the test all barrels were pulled, cleaned and inspected for throat erosion and heat cracking. In the end, The ABS barrels had roughly 8 thou less throat erosion(throat length) then the Lilja barrels but they were identical, within +/- 1 thou of the Krieger. Heat cracking appeared to be nearly identical in all barrels.

From this torture test it was clear that if you mistreated ANY barrel with a chambering like this, you would not be saved by a very high dollar barrel which is advertised to offer dramatically longer barrel accuracy life. Just not the trueth.

I have also tested a couple rifles shooting them as they should be, this time both were in 7mm Allen Magnum. One was a Lilja 1-9 4 groove, #8 contour, 30" fluted barrel, the other an ABS 30" 1-8.7, 5 groove, similiar contour to a #8 with Rock sleeve.

Both rifles were shot and cleaned regularly, never more then three shot strings. Noticable accuracy drop off started at around 850 rounds with the Lilja, around 925 rounds with the ABS so yes, the ABS offers longer accuracy life but this is I am sure simply due to the different hardness of steel used in the cut rifled barrel compared to the much softer steel used in the button pulled Lilja.

Still, 75 more rounds for over twice the cost of the barrel was not worth it in my opinion.

I believe the ABS barrels are the very best barrels out there for a carbon wrapped barrel. They do shoot very well, in some applications they do offer significant rifle weight reduction but if used in the wrong application, they really do not offer much over an all steel barrel.

Just my findings."
__________________
Kirby Allen

Followed by this on the same thread:

Darin, you are absolutely right as to the fact that the lay up is critical. There are several different methods of laying carbon fiber to get what you need. For example, a 45 degree lay up is strictly used for torsional stiffness. An 89 degree is used for hoop strength and a shallow angle will help against barrel whip by increasing stiffness. Also, we have found that in a lightweight build they are more accurate than a standard stainless or cro-mo barrel. On our Kifaru Rambling Rifles we started with a Krieger #1 cro-mo 5R 20.75" in 308 and our best 3-shot groups were about 7/8" (2 overlapping holes and short flyer) in a rifle weighing 4# 14oz. We had an engineer who is a pretty big name in the military world (actually worked on Skunk Works) come in and work with our engineers to lighten up the barrel and increase stiffness. It is correct that a carbon barrel and a steel barrel of the same contour, the steel will be much stiffer. However a barrel of similar weight the carbon, assuming the layup is correct, will be much stiffer. Carbon is roughly 1/5 the weight but only (depending on type of fiber, and layup) can be much closer in strength than just 1/5. Thus giving it a much greater strength to weight ratio which is where the rumors come from. After we turned down and carbon wrapped our barrel we ended up with a lighter barrel that is capable of consistently shooting .5" groups (100yd) and Patrick Smith actually shot a 5/16" 3 shot group with factory match ammo.

Another rumor that's out there, thanks to some barrel manufacturers is their claim of thermal conductivity and heat dissipation using pitch fibers. It's true that pitch fibers have outstanding thermal properties however when laid in any manner other than perpendicular to the material needing to be cooled have the same effect as an insulator. the trade off is that if you somehow are able to lay fibers in a perpendicular manner you will be sacrificing strength. Also you need a place to transfer the heat. Heat does not just go away, it needs convection, it needs a place to go. Do not believe anyone telling you that carbon wrapped barrels actually dissipate heat faster than steel. The real weak link is the resin.

The true craftsmanship on carbon builds comes in dealing with heat expansion and contraction. Trying to get everything (steel, carbon, resin and harmonics) all happen in concert with each other is the trick because everything happens at different rates. On hunting rifles it's not a big issue but in a tactical scenario if you needed to lay down suppressive fire and maintain accuracy then it can be hard. There are resins that go up to 1000 F but still hold heat in the steel barrel and because carbon actually moves more at temperature you will see your shots walk. We actually wrapped a way to thin carbon barrel and shot it as fast as possible with a bolt gun and watched as the first 2 shots were tight then the following opened up to almost 5" and then after about 8 rounds the group started to tighten up again. Pretty funny behavior for a barrel to do, but damn, I love my job.

The way we have found to maintain accuracy is by a de-bulking process and proper lay up. We try to maximize hoop strength and barrel stiffness. It helps to use cut-rifled barrels that have been cryo-treated, nicely lapped (preferably after turning). Also, cro-mo barrels have a much greater hoop strength than stainless if you turn them down to minimum wall thickness. Especially in cold temps. Either one can be done safely with a proper safety factor. Another nice fact about carbon fiber is that it maintains it's strength in all temps. It is inert which is why NASA uses it in outer space.

So, yes, based on our experience, carbon wrapped barrels can be worth it depending what you are looking for. If weight is not an issue go steel. If you are trying to minimize weight while trying to maintain stiffness then go carbon. It's not just about cool factor or some pointless beauty layer on the outside of a barrel, it can actually perform a task. That's pretty much why the stuff exists. Carbon fiber is very neat stuff.

Thanks guys. No real diffinative answer really. It seems there is no rule of thumb and carbon can be lighter but at a cost of stiffness. Having said that it can be very close depending on quality and the manufacturing process used.

Just to note
Abs barrels is now apart of proof research

Sent from my SM-G935F using Tapatalk

Originally Posted by 199p

Just to note
Abs barrels is now apart of proof research

Sent from my SM-G935F using Tapatalk

Kirby's post is just over 5 years old & things have changed a little since then

Carbon wrapped barrel ? | Long Range Hunting Online Magazine

ABS is now Proof Research, they use cut barrels, I'm not sure who makes them, I think they do.

IIRC ABS used to use Benchmark & Rockcreek barrels.

Benchmark are making Carbon barrels and apparently Rockcreek are going to be soonish as well.

The American & the Kiwi ideas on "lightweight" are quite different

I'm having good results from my Hardy carbon 7mmRM. 5 rounds @ .17 of an inch at 100 yards, using 162ELD-M @ 3017 fps.

Originally Posted by kiwiazonic

I'm having good results from my Hardy carbon 7mmRM. 5 rounds @ .17 of an inch at 100 yards, using 162ELD-M @ 3017 fps.

Pics please

Originally Posted by kiwiazonic

I'm having good results from my Hardy carbon 7mmRM. 5 rounds @ .17 of an inch at 100 yards, using 162ELD-M @ 3017 fps.

Yes pics

Originally Posted by kiwiazonic

I'm having good results from my Hardy carbon 7mmRM. 5 rounds @ .17 of an inch at 100 yards, using 162ELD-M @ 3017 fps.

You must had a good one then,I only managed that with the first three shots after that things turned to shit really fast,wouldn't have another Hardy carbon if you gave it to me,no offence just my experience

I thought the main purpose of carbon wrapped barrels was the separate the average punter from the contents of his wallet

Originally Posted by kiwiazonic

Attachment 72776
Attachment 72777

Nice group and nice rifle.
What do you think of the VX6HD? Are the turrets any good?

Originally Posted by Beetroot

Nice group and nice rifle.
What do you think of the VX6HD? Are the turrets any good?

It's a nice lightweight scope 550-600 grams. clicks are ok, not as defined as the nightforce scopes. I do like the zero locks and dual rotation 38moa elevation turrets.
Glass is good-great, again there is better on the market.

If someone was asking, I would say have a close look at the VX-5HD or Vortex Viper PST Gen2 before considering a VX-6HD, they are much cheaper and glass almost as good.

I'm happy with the scope and rifle setup, now I need to take it to the hills so it can earn it's keep.