6.5 PRC Build - Barrel Length and Twist

[jw-usmc]

Starting my first 6.5 PRC build and looking for advice on barrel length and twist selection.
Building on a new Zeus action from Terminus and I'm between a 24 or a 26 inch barrel with a 8 or 7.5 twist. Any thoughts or advice one way or the the other?

Heard some great results from the factory ELD-X and ELD-M selections, but may be venturing out with the release of the Berger 156s.


Thanks for the help.

 

[jw-usmc]

I read through this thread and a few others:

https://www.snipershide.com/shootin...out-the-6-5-prc-and-how-to-build-one.6916097/

Still curious if anyone has any updates or advice, particularly with the 156 Bergers in mind?

 

[762 ULTRAMAGA]

Definitely go at least 7.5 twist if you plan on using the 156.
I'm shooting 147's in my 6.5 saum, it's an 8 twist but I wish I'd gone with a 7.
I'm getting 3050 using H1000 with the 147's from a 25" barrel.

 

[Kickin45]

26” 7.5 twist maybe even 7.25 if going with the 156’s

 

[jw-usmc]

Definitely go at least 7.5 twist if you plan on using the 156.
I'm shooting 147's in my 6.5 saum, it's an 8 twist but I wish I'd gone with a 7.
I'm getting 3050 using H1000 with the 147's from a 25" barrel.

Got it. Great numbers on your 25". How many rounds do you have through the barrel? Running suppressed or brake?

 

[jw-usmc]

26” 7.5 twist maybe even 7.25 if going with the 156’s

Thanks for the advice. Would you stick by the 26" if running suppressed?

 

[Kickin45]

Yup.
With this round, barrel length is your friend.
I built mine with a 28” 1-7.75 and I run it suppressed. Shoots the 143’s like a laser.

 

[Cascade Hemi]

I went with 30" 1:7.5. Casual 3100+ with 150 class bullets is the goal.

 

[Ledzep]

Consider this, for a 7.5" twist: 12 / 7.5 * 3000 * 60 = 288000 RPM. For a 7.25 twist it's 298k rpm. 7 twist is 309k. Add in a rough throat or carbon ring because "don't clean it until accuracy falls off" and 200-500 rounds later you're blowing up every non bonded bullet on the market.

An 8 twist at 3000fps keeps you well below 300,000 rpm, and still provides a 1.3 SG at sea level and 0 degrees F with a 156 EOL. At normal temperatures and any significant elevation above sea level it boosts up well over 1.5. The PRC does not need, and has never needed for any projectile I'm aware of, anything faster than an 8 twist.

 

[samson7x]

Slight thread drift, what freebore to you folks recommend? Will factory Hornady chamber in .154 freebore without hitting the lands?

 

[jw-usmc]

Consider this, for a 7.5" twist: 12 / 7.5 * 3000 * 60 = 288000 RPM. For a 7.25 twist it's 298k rpm. 7 twist is 309k. Add in a rough throat or carbon ring because "don't clean it until accuracy falls off" and 200-500 rounds later you're blowing up every non bonded bullet on the market.

An 8 twist at 3000fps keeps you well below 300,000 rpm, and still provides a 1.3 SG at sea level and 0 degrees F with a 156 EOL. At normal temperatures and any significant elevation above sea level it boosts up well over 1.5. The PRC does not need, and has never needed for any projectile I'm aware of, anything faster than an 8 twist.

Great advice and thank you for the equation. Helps a lot.

 

[Another Casual]

I'm happy with my 26 inch 1in8 barrel, but I'm running 140 accubond for hunting. Only 150 rounds through it, but able to hit 3100 with the 140 and H1000, but my node looks to be closer to 3050. Ok sure RL26 (if you can find it) will get you 3150 fps with 140.

 

[Cascade Hemi]

Consider this, for a 7.5" twist: 12 / 7.5 * 3000 * 60 = 288000 RPM. For a 7.25 twist it's 298k rpm. 7 twist is 309k. Add in a rough throat or carbon ring because "don't clean it until accuracy falls off" and 200-500 rounds later you're blowing up every non bonded bullet on the market.

An 8 twist at 3000fps keeps you well below 300,000 rpm, and still provides a 1.3 SG at sea level and 0 degrees F with a 156 EOL. At normal temperatures and any significant elevation above sea level it boosts up well over 1.5. The PRC does not need, and has never needed for any projectile I'm aware of, anything faster than an 8 twist.

There's reports of 150 SMK going sideways out of 6.5-284 with 1:8. There's nothing special about 6.5 PRC, it's pretty much the same as 6.5-284 and 6.5-06.

 

[Ledzep]

I hadn't ever heard that before. I've shot 150 SMKs, 156 EOL, 153 A-tips, 147 ELD-M all through a couple 8 twist PRC's and SAUMs and never a hint of stability issues.

I'd guess those barrels are on the taller end of 1:8 twist. At any rate the best advice to the OP is to widely educate yourself and choose accordingly. Personally, I favor the slowest reasonable twist possible in almost all cases where over-spinning may be a concern (I.e. near 300k rpm). At some point with small(er) caliber overbore cartridges you have to weigh being able to shoot the longest bullet on the market against creating a scenario that 200-800 rounds later is going to cause frequent blow-ups with basically all match bullets. FWIW, I always suggest 5r rifling in such cases.

 

[762 ULTRAMAGA]

I hadn't ever heard that before. I've shot 150 SMKs, 156 EOL, 153 A-tips, 147 ELD-M all through a couple 8 twist PRC's and SAUMs and never a hint of stability issues.

I'd guess those barrels are on the taller end of 1:8 twist. At any rate the best advice to the OP is to widely educate yourself and choose accordingly. Personally, I favor the slowest reasonable twist possible in almost all cases where over-spinning may be a concern (I.e. near 300k rpm). At some point with small(er) caliber overbore cartridges you have to weigh being able to shoot the longest bullet on the market against creating a scenario that 200-800 rounds later is going to cause frequent blow-ups with basically all match bullets. FWIW, I always suggest 5r rifling in such cases.

I can tell you from personal experience that a 140 cutting edge MTAC will keyhole from an 8 twist at 3100 fps.
A 156 will have marginal stability at best, I sure wouldn't do it

 

[gnochi]

Huh, that’s an interesting observation. As BC goes up, via lengthened bullet, you hit a point where you must go monolithic to survive the twist rate that gives you stability. Sounds like the cutting edge modern stuff (full pun intended) is right on that edge.

 

[6brshooter]

I shoot 147eldm in a 20" 6.5 creed 8tw at 2730fps, no stability issues.

 

[762 ULTRAMAGA]

Got it. Great numbers on your 25". How many rounds do you have through the barrel? Running suppressed or brake?

I have approx. 350 rounds through it, no brake or suppressor it's my lightweight LR hunting rifle.
I will say though, when I burn this barrel out I'm going with a 20" 7 twist that I'll run suppressed.
It'd be awesome to take quick hearing safe shots in the timber, and still be able to spot long shots

 

[TreyMeTrey]

Yup.
With this round, barrel length is your friend.
I built mine with a 28” 1-7.75 and I run it suppressed. Shoots the 143’s like a laser.

what is your velocity suppressed with you 6.5 PRC and 28 inch barrel and 143's? Im wanting to build one and getting info? would you stay with what you have since this post is a few years old? thanks

 

[SmokyJoe]

I am having good success with the 156 EOL @ ~2,940fps through a 24” Bartlein 5R with 7.75 twist. Also great with Hammer Hunter 124gr solids @ ~3,150fps.

 

[TreyMeTrey]

I am having good success with the 156 EOL @ ~2,940fps through a 24” Bartlein 5R with 7.75 twist. Also great with Hammer Hunter 124gr solids @ ~3,150fps.

Okay.Thank you.The 3150 is about where Id like to be incase of a hiccup .I dont want to go past 3200

 

[TreyMeTrey]

Okay.Thank you.The 3150 is about where Id like to be incase of a hiccup .I dont want to go past 3200.. How far are you shooting with yours?

 

[SmokyJoe]

Out to 300Y in load dev so far.

 

[TreyMeTrey]

Ok.Thank you. Ive just been reloading about 1 year.Still learning alot.I got into long range shooting.I was and still do some..Shoot my 6.5 Creedmoor.But changed over to 6.5 PRC and want to build a nice Competition rifle in 6.5 PRC for F class. I di not want to shoot a 308 so chose the 6.5 PRC to shoot in open class. Thank you for the help.

 

[NDSU]

Factory Bergara HMR. 24” 8 twist barrel. Loves RL 26 and 142 gr ELDMs.