Rem 700 VS Composite

[RifleMaster]

There is an article in the March "American Rifleman" on the new Remington Model 700 VS Composite (composite bull barrel) rifle. The authors of this article make some claims about barrel cooling that wasn't in my Thermodynamics text! The bottom line is that for a "suggested retail price: $1,865" you get a Rem. 700 with a lighter "heavy/rigid" barrel! If you guys believe that the heat energy of a fired round will conduct to the outer surface of this composite barrel so fast that the outer surface becomes hotter than the inside surface, well, then I have a beach front property deal for you!

Hold'em hard!

RifleMaster

[JY]

Hi Carl;

Good post buddy 8) I like seeing myths destroyed, to bad the lighter barrel also destroys the heavy barrel holding advantage.

takle care...Jim

[RifleMaster]

Hi Jim,

The rigidity of the Remington composite bull barrel comes from its full 1.25 inch diameter. I doubt if this new composite barrel is more rigid than a standard #7 contour (1.2" X .875") steel target barrel. Most graphite fiber filled epoxy doesn't have the strength of steel. When a rifle is fired, the highest stresses are created at the receiver end of the cantilever barrel. Barrel whip can be reduced by increasing the barrel strength at the receiver end. This new composite barrel is mostly stainless steel on the receiver end!
I wonder how many times these composite barrels can be set-back. Probably not!
I think Remington could cast Aluminum around their stainless steel core and achieve a greater strength to weight ratio.

Carl/RifleMaster

[RifleMaster]

Hi All,

Yesterday, I was surprised to fined that graphite epoxy composite does have a very high ultimate strength! So, my above statement was WRONG about the relative strength! I would like to know the properties of the specific graphite epoxy used.

My statement about how heat is transferred (flows) is correct. Again, I would like to know the thermal conductivity of the specific graphite epoxy used. Graphite has a conductivity about 4 times that of barrel stainless steel and unfilled epoxies have a conductivity 24 times lower than barrel stainless steel. The actual blend will determine the thermal conductivity. Today, if I have the time, I'll look-up the properties of some specific graphite epoxy.

Carl/RifleMaster

[This message has been edited by RifleMaster (edited 03-21-2000).]

[Cut]

My understanding of the composite barrels are a metal tube with the carbon fiber surrounding the tube for support.

This seems all well and good til one is hotter than the other and expansion rates apply to the different matterials.

I would expect separation between the tube and carbon fibers and inducing stresses at various points on the tube. Along the lines of a bent barrel, only its bent on the inside and undetectable from the outside.

Does this mean that the Remington and other composite barreled guns should be reduced to a very slow rate of fire in order to make the barrels last as long as possible?

I don't know what the expected barrel life would be for a composite barreled rifle.
Be interesting to see how they compare to traditional steel rifle barrels.

[Mac679]

on the subject of using composites and the question of their strenght keep in mind where this technology has been used: mountain biking; I don't think someone's gonna put a rifle barrel through half the things a mountain biker puts their bike through, like jumps where you have a 180lb rider crashing back down on to the seat upon landing, crashes themselves, and hitting 60mph in downhill races; I don't think strenght or rigidity will be a problem and since carbon fiber is lighter than steel it might prove useful on .50 rifles allowing more ammo to be carried ( not that carrying a .50 for 20 miles is a bright idea to begin with :-)
I don't know about the materials hitting different temps, definitely something that needs to be investigated thoroughly, but as for material seperating, it depends on the epoxy used to bind them, but some of that stuff is used in applications where high temps are expected ( I do believe it's an epoxy used to hold the heat resistant tiles on the space shuttle-the tiles might protect from the heat but epoxy will definitely be stressed ); all in all I think it seems for the most part like a good concept that needs some more testing and refining
Just my 2 cents,
Mac

[RifleMaster]

Hi Mac,

You are right, I/we should not be too hard on Remington for doing some Research and Development (R&D)! The article mentioned above wasn't written by a Remington Engineer!

Having humped a BAR, M60, and PRC-25, I think light is goooood!

Take care!

Carl

[Mac679]

LOL@the BAR comments
definitely sounds like a great concept when they get the bugs and potential field problems worked out
be as hard on it as you want, you've got the experience to know pork when you see it, as well as pros and cons.
Later!
Mac