Point of impact shift with carbon fiber wrapped barrels

[Shane Lindsey]

I too have noticed this. My 300 RUM is good for about 5 shots, relatively slow anything after needs a good bit of time before or it tends to get loose.

6.5 Creedmoor, 308 Win, 7 Rem Mag, 300 WM all did the same. The smaller ones not as fast, but can't shoot strings of ten in less than five minutes.

On another note, mirage gets crazy bad coming off the carbon barrels.

Hunting barrels, all are good for a cold bore and follow up if needed.

 

[lancetkenyon]

In the field, unless your on a prairie dog town, no reason to shoot 6 rounds.

But I do know of a few people that are using carbon fiber wrapped barrels as combination hunting/F-Class rifles. (20 shot strings)

Probably not with 300PRC though.

 

[bultinkle]

I would call bart and talk to Frank. I may be wrong but I really thought Frank had his own carbon barreled 300

 

[Radman]

I have a custom build in 300 PRC with a Bartlein Bull Sporter #4 CFW barrel. Have completed load development. After 6 rounds or so, POI seems to shift up and to the right (consistently). It goes from sub MOA (for 3-4 shots) to about 2 MOA. I'm waiting about 1-2 minutes between shots but the barrel still gets quite hot. Is this shift to be expected? Have I damaged the barrel? Is a POI shift to be expected with CFW barrels?

With every barrel I've ever had that crawled/crept it was always upwards-right, (two of them making an actual question mark).
IMO: A carbon wrapped barrel is great for making an accurate hunting rifle lighter & less of a burden to carry. I believe that they are meant for/great for hunting.
This gets back into zeroing for the cold shot verses zeroing a warm barrel. I think most folks learn that a cold zero IS what you want for hunting. A target rifle that may spew anywhere from 3 - 300+ rounds (dependent on caliber) is often zeroed for the follow up shots. (You already know this) With that in mind - with carbon wrapping two entirely different materials are married together and I personally do not see how the two can expand, (from heat), at the same rate. (Coefficients of thermal expansion) Now: On top of that I believe that barrel "whip" becomes more obvious with successive shots. If you hunt (any barrel) with a carbon-wrapped, IMO, zeroing your 1st cold shot is of paramount importance. I don't think there's anything wrong with your rifle. Again....just my opinion.
.

 

[Im4u2nvrc]

I have a Christensen Arms 300 PRC MPR (CWB). I first noticed the same thing with my shot groups compared to my friends Bergara 300 PRC (Steel Barrel). The warmer the chamber, the more the next bullet's muzzle velocity was thrown off. I talked to some old veteran shooters about our issues. They said I was "pre-cooking" my rounds. The extra chamber heat changes the ignition speed of my powder. If I let it cool down between shots, I didn't have a problem.

 

[82nd Bill]

I have a custom build in 300 PRC with a Bartlein Bull Sporter #4 CFW barrel. Have completed load development. After 6 rounds or so, POI seems to shift up and to the right (consistently). It goes from sub MOA (for 3-4 shots) to about 2 MOA. I'm waiting about 1-2 minutes between shots but the barrel still gets quite hot. Is this shift to be expected? Have I damaged the barrel? Is a POI shift to be expected with CFW barrels?

I have several CF rigs and they all creep with heat (3-5 rds). CF is not cooler but it dissipates the heat a little better then steal. That said you are generating a tremendous amount of heat with a 300 PRC and 1-2 minutes is not nearly enough time to cool.
When I zero I want to know the cold bore and the follow-up shot. those are the important ones, and I zero the cold bore. My smaller calibers have nearly no creep and my 7 SAUM and 300wsm have a .25" shift on those two shots. Great hunting group.
Check your float to be sure and if it is a lightweight stock don't rest it on or near the front end as it can flex and change the POI. Remember it is a hunting rig and not a competition rig.

 

[rbuoncri]

I would call bart and talk to Frank. I may be wrong but I really thought Frank had his own carbon barreled 300

I have an email into them. Hope to hear back next week.

 

[VinceMule]

Barrel makers are dramatically reducing the dia of the barrel prior to putting the carbon wrap on it, you take your chances on warping, and many of the issues are related to the barrel blank as it came from the foundry.

With the carbon wrap on the barrel, ever think of just how well the barrel actually cools?

 

[FullCurl8]

I have a Christensen Arms 300 PRC MPR (CWB). I first noticed the same thing with my shot groups compared to my friends Bergara 300 PRC (Steel Barrel). The warmer the chamber, the more the next bullet's muzzle velocity was thrown off. I talked to some old veteran shooters about our issues. They said I was "pre-cooking" my rounds. The extra chamber heat changes the ignition speed of my powder. If I let it cool down between shots, I didn't have a problem.

I have never seen a chamber increase much in temperature, it only receives radiant heat. I think you were given poor info there.

 

[VinceMule]

Shooting p. dogs, Rock Chucks, and jackrabbits, I have seen pressures skyrocket when rounds were left to cook in the bore and for this application, Temp insensitive powders really show their worth. We were dumping out boxes of 50 rounds and firing as fast as we could single load and acquire targets, 223-243 AI.

 

[Joefrazell]

Make sure there's no bedding after the lug

 

[Shane Lindsey]

With the carbon wrap on the barrel, ever think of just how well the barrel actually cools?

I have come to believe it doesn't. It's like wrapping it in a sleeping bag.

 

[7.62 Gunner]

I have come to believe it doesn't. It's like wrapping it in a sleeping bag.

100%
I dabbled with CF barrels for a bit and quickly moved back to light contoured steel.

 

[kgunz11]

Take any #3 contour barrel and shoot 6 rounds of 300 PRC and I promise you the groups will start to walk from heat. There's nothing wrong with the barrel, the carbon wrap, the rifle, or the ammo. It's just how the steel responds to getting that hot. They claim CF dissipates heat faster, but independent testing has proven that Carbon Fiber wrapped barrels hold heat longer than a steel barrel of the same size.

I like carbon wrapped barrels for what they are. I build guns with a bunch of them, and I know their limitations.