6.5 PRC Barrel Questions

[parshal]

No, there is not a performance reduction. If you shoot near sea level the extra twist will ensure stability. Use Berger's stability calculator to determine if it's stable enough at different altitudes. Velocity is a factor, too.

8 twist barrels will work for most everything other than the long bullets at lower elevations. They're also much easier to find than a 7.5.

<edit> I use the 153.5 in my 6.5 Creedmoor for NRL Hunter. I run it at 2580 'ish. At sea level, stability is marginal in an 8 twist. 7.5 twist is stable. At 3000 fps it's more stable but still on the high end of marginal in an 8 twist. In order to be stable, according to the calculator, I need to be above 2500' elevation. I may shoot matches below 3000' elevation and will be hunting around 4000' in Africa with the 156..

 

[lancetkenyon]

Terminal performance.is said to be better with a faster twist rate.
The 150 SMK states 1:7" minimum twist. A mono over 130gr states faster than 1:8".
Stability deteriorates as speed deteriorates. Faster twist helps retain stability longer.
No reason NOT to go 1:7.5" if you plan for any of these during a new build/rebarrel. But if you already have a 1:8", you usually don't need to swap until it is time.

 

[Squatch]

I have a factory Proof MTR. They put a 1-7.5 on it. It shoots fantastic.

 

[JuddL]

The faster twist is going to be slower speed but not by large margin (less than 50fps). Lance is right, the spinning of the fast twist seems to give the edge to terminal performance.

The 7.5 will limit you on the bottom end as you can spin the light bullets fast enough to rip jackets off.

 

[CMP70306]

I'm working on a 6.5 PRC. I'd love some feedback on a few barrel questions. Really looking for light weight but don't want to sacrifice any accuracy.

I really want a 22" barrel and understand the velocity difference compared to a 24". The question is, is there an accuracy difference between 22" and 24" barrel?

Leaning towards Proof vs Bartlein for weight, but i've read some info about the Proof 4 groove. It seems like there is a lot of positive feedback on the Proof 6.5, so is it really an issue? I'd like the cut rifling, but if a 4 groove is inferior, should Carbon 6 be considered?

Is Sendero Light contour adequate, or is Sendero needed to maximize accuracy? Or does the contour even effect accuracy?

Thanks in advance for your feedback.

My Carbon 6 18" Magnum contour 6.5 PRC is 36 oz while my dads featherweight contour is 33 oz. Currently shoots the 130gr Berger OTM at 2980 fps and the 123 Absolute Hammer around 3100.

I didn't see any significant change in accuracy from a 26" barrel down to a 16" in a test I did.

What was the velocity difference between the two?

 

[parshal]

My experience with velocity differences with different twists.

56 grains R23 in a 7.5 twist 65SS gave me 3215 with the 124HH and in an 8 twist 56.1 gave me 3231. Both were 26" barrels but one was a steel Brux and the other a Proof carbon.

The only other direct comparison I have with twists had a 2" different barrel length so it's not apples to apples.

Personally, I think each barrel being different in and of itself is more of a factor for velocity difference than the twist rate when we're talking 8 vs 7.5.

 

[vancewalker007]

What is the reason to not use 7.5? Is there a performance reduction with the faster twist?

In general, there would likely be not noticeable difference in the 2 with most cup and core bullets. There were some issues being reported with 1:7 barrels causing bullet failures using the Hornady 147 ELDMs. Some of the monos, like Hammers have recommended higher twist rates on some of their bullets. So, there may be some pluses and minuses depending on what bullets you're shooting.

 

[rbwv23]

I'm working on a 6.5 PRC. I'd love some feedback on a few barrel questions. Really looking for light weight but don't want to sacrifice any accuracy.

I really want a 22" barrel and understand the velocity difference compared to a 24". The question is, is there an accuracy difference between 22" and 24" barrel?

Leaning towards Proof vs Bartlein for weight, but i've read some info about the Proof 4 groove. It seems like there is a lot of positive feedback on the Proof 6.5, so is it really an issue? I'd like the cut rifling, but if a 4 groove is inferior, should Carbon 6 be considered?

Is Sendero Light contour adequate, or is Sendero needed to maximize accuracy? Or does the contour even effect accuracy?

Thanks in advance for your feedback.

I recently had a custom 6.5 PRC built with a Proof sendero light finished at 22" with a 1:7.5. Accuracy isn't an issue. However, the gunsmith did recommend going to the sendero if I was going to go with any caliber bigger than the 6.5.

 

[CMP70306]

Came up with a load for my 18" Carbon six barrel, 54.5gr H4350 behind a 130gr Berger OTM gives me 2980 fps. It was a warm load but rounded primers and no bolt lift or extractor marks. I took that same load and put it in another 18" carbon six barrel, the only difference being the twist rate and got heavy bolt lift, major ejector mark and 3150 fps.

This other Carbon six barrel has been nothing but trouble as it doesn't shoot that well and it has to be downloaded significantly compared to every other 6.5 PRC I own. This is an issue since my Dad, Brother and I all shoot 6.5 PRC and I don't want to load ammo that will almost lock up my Dad's rifle in the event he grabs one of my mags even though the ammo is perfectly fine in mine and my brother's rifles.

 

[Rok1167]

Took me a while but proof prefits are limited to sendero and 24" or 26" so a gunsmith has to do a sendero light. I have a bartlein cf #4 and it's about the ideal contour for my liking, even smaller than the sendero light. The prefit at sendero contour simplifies things a lot, and is a fair amount less expensive. Sendero going to look ok on a manners MCS-T? They seem so fat

1-2 Oz heavier as well, which is also not ideal. For some reason Proof actually said they always recommend the sendero if the stock can take it.

Thoughts? Prefit to simplify things, or more expensive custom sendero light for 2 Oz and preferred appearance? This is for a lightweight carry/hunt application.

 

[StanleyActual]

I'm working on a 6.5 PRC. I'd love some feedback on a few barrel questions. Really looking for light weight but don't want to sacrifice any accuracy.

I really want a 22" barrel and understand the velocity difference compared to a 24". The question is, is there an accuracy difference between 22" and 24" barrel?

Leaning towards Proof vs Bartlein for weight, but i've read some info about the Proof 4 groove. It seems like there is a lot of positive feedback on the Proof 6.5, so is it really an issue? I'd like the cut rifling, but if a 4 groove is inferior, should Carbon 6 be considered?

Is Sendero Light contour adequate, or is Sendero needed to maximize accuracy? Or does the contour even effect accuracy?

Thanks in advance for your feedback.

You won't go wrong with Bartlien or Proof. Bartlien leaves a little bit more metal on the barrel before wrapping which is why it's slightly heavier and also makes it a bit stiffer. Some people see that ad an advantage.

-Length has nothing to do with accuracy. Only Velocity.

-Barrel Contour makes for a stiffer barrel and takes a bit longer to heat up before accuracy starts to shift.

Photo below top is a 22" Bartlien CF Sendero lite in 308

Bottom is a 16.5" Proof CF Sendero in 6.5CM. This action also gets a 22" Proof Sendero in a 6.5PRC

Both come in at about 8lbs as they sit in that photo (Bighorn Origin SA, Hawkins Precision BDL, Mesa Precision Altutude stocks.

I also have (2) 24" proofs in 7RM and another 22" in 6.5PRC.those are all
in a the Sendero (M24) contour. I'm a big fan of Bartlien and if their CF barrels were as available as the Proofs, that's probably the route I would have gone. Not saying anything at all is wrong with Proof. Just
my barrel preference.