I’m looking at doing a rebarrel on my S20 6.5 PRC. 1-8” is to slow for long bullets and I’m thinking of going all they was to 1-7. Anyone have any thoughts on this? Is it to fast? Looking at HORNADY 143 eld-x or Berger 156.
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If 156's are on the menu, I would spec a 1-7 without hesitation.
I've had both 1-8 and 1-7 and they both worked well with everything I've shot. I've only gone up to 147s on the 1-8 though.
Next stick will be 1-7 just because...
Next stick will be 1-7 just because...
How long is the barrel? 1:8 will stabilize 150's with enough velocity. I have a 1:7.5 pushing 150's 3025fps, stability isn't an issue.
This is a good point - my perspective is shorter barrels in the bitter cold with pressures well under max. Hence my preference for faster twists.
I've run a few thousand 153.5s and 156s in a 6.5 Creed and 1:7.7 twist at ~ 2680-2700 fps. Haven't had stability issues out to a mile in 20 degree temps and 400' elevation. 1:7 seems overkill to me. 7.5 or 7.7 would be my go to
Do we have to guess the barrel length and conditions you have in mind or are you going to tell us? It's pretty doubtful you'd download 6.5PRC to the point 150's are too slow for 1:8 unless you talking about an SBR. You for sure can over spin them until they come apart though. 1:7 6.5 barrels are mainly for slow 6.5 with 150's, not 6.5PRC/6.5-284/6.5-06.
Yeah, also skeptical over here that it’s necessary. Let’s hear the bullet and expected MV, OP
1:8.5 in a creedmoor will have issues with some of the super heavies. 1:8 in a creedmoor or PRC is fine for pretty much everything on the market. 1:7 is overkill.
If you shoot in especially low altitude cold weather often, I could see maybe a 1:7.5" if you're scared but I still don't totally believe it's "necessary".
If you shoot in especially low altitude cold weather often, I could see maybe a 1:7.5" if you're scared but I still don't totally believe it's "necessary".
1:7 works fine for most stuff in the 6.5 PRC. I did have 153 A-Tips start blowing up after about 1200 rounds on my last barrel. The Berger 153.5s have never had a problem. I also never had a problem with the Hornady 147ELDs either, but did not shoot them as much. I shoot all of these in the 2950-3050fps range.
…or you could go 1:8 and blow up less bullets?
Or just not use Hornady bullets which have known problems with blowing up. The Berger 153.5 LRH bullets shoot just as well as the 153 ATips and have no such problems. And 1:8 twist is marginal for stabilizing bullets in that class. But it really depends on what you want to shoot, 1:8 will work for a lot of stuff. I started with a 1:7 because it was what Marc at SAC recommended, and really have not had a good reason to re-consider.
I’m wanting
26 inch barrel. Will usually be over 1500 feet above sea level and between -10c and +18c.
Have you consulted this?
bergerbullets.com
I shoot 147 ELDMs at 3000 out of a 1:8" with no issues but I'm at 6000ft and usually around 30 to 60*
Twist Rate Stability Calculator
Our newly updated Twist Rate Stability Calculator not only tells you what your SG is, but it also lets you know if you are reaching your optimized BC.
bergerbullets.com I shoot 147 ELDMs at 3000 out of a 1:8" with no issues but I'm at 6000ft and usually around 30 to 60*
Fwiw, Berger says most of their bullets will handle “up to 300k RPMs.” For certain bullets, especially if you call and talk to them, they’ll be like “300k *wink wink*.”
I’ve tested .224 85.5s in a 6.5t up to 355k RPMs (in a 28” barrel) without failure. Obviously not a 1:1 comparison, but bottom line is while they say 300k, and while I’m sure that there are certain bullets that will shed jackets around 300k, I think others will go higher.
I know that Berger has also started using thicker jackets in some of their designs because assholes like us like to make things as difficult as possible. I run a 1:7t 6.5x47L with 153.5s, but it’s really slow (~2600fps), so I don’t really have any concerns about blowing jackets apart.
All that to say, is a 7t probably unnecessary in PRC? Yes. Can you probably get away with it? Also yes.
I’ve tested .224 85.5s in a 6.5t up to 355k RPMs (in a 28” barrel) without failure. Obviously not a 1:1 comparison, but bottom line is while they say 300k, and while I’m sure that there are certain bullets that will shed jackets around 300k, I think others will go higher.
I know that Berger has also started using thicker jackets in some of their designs because assholes like us like to make things as difficult as possible. I run a 1:7t 6.5x47L with 153.5s, but it’s really slow (~2600fps), so I don’t really have any concerns about blowing jackets apart.
All that to say, is a 7t probably unnecessary in PRC? Yes. Can you probably get away with it? Also yes.
300K I'm a new barrel or 300K 1200rds in are two different things tho
1:8 is more than enough. I have a hard time keeping A-Tips together with 1:7.5. I stopped shooting Hornady bullets in it all together.
It’s another factor to consider, sure, but no different than bullet selection or velocity. Hornady bullets are more likely to shed jackets than Berger, just like you’re more likely to blow them up at 3100 than 2800. Same thing for a new barrel vs one with 1200 rounds.
The point is that I think a 1:7t PRC can be made to work fine given the right combination of those things. It’ll never be optimized, but certainly not dead on arrival.
If you shoot shitty hornady bullets, yes. Not with a quality bullet like Berger or Sierra.
147's do really well on game tho. And if your elevation allows it, you won't see any issues in a 1:8". I also wouldn't malign Hornady alone for these issues. Berger and Sierra have both seen issues with blowing up bullets in these extreme twist/ rpm barrels as well. The 150SMKs especially. What you're trying to define as the "right combination" is actually a narrow sliver of compatibility.
RPMs are agnostic of caliber.
MV x (12/twist) x 60 = rpms
A 1:7" in a cartridge with enough ass to push a given bullet over 300K rpm puts bullets in a vulnerable position. Berger may marginally be better but you're pushing the ragged edge and in reality you won't know if and when your barrel starts blowing up bullets.
I shot in the same squad with a guy shooting a 22-250AI in 1:6.5". 95SMKs over 3000fps. I asked him if he ever had any issues with bullets coming apart. He confidently replied, Nope. And 1800rds on the barrel too. Three or four stages later, as the day heated up, he fired his first round on a stage. Easy target at 280yds or something. Flat out miss. Nobody saw splash or dirt. At that point I just stood directly behind him and watched out in front of his gun target line. He fired the second round and a grey puff appeared about 50yds out. I told him his bullet blew up. He didn't believe me but still couldn't figure out why he had a flat out miss and no dirt or splash. He never accepted it.
I think that's a pretty good parable about people who are confident in their 1:7" speed cartridges.
It's not a problem. Until it is.
RPMs are agnostic of caliber.
MV x (12/twist) x 60 = rpms
A 1:7" in a cartridge with enough ass to push a given bullet over 300K rpm puts bullets in a vulnerable position. Berger may marginally be better but you're pushing the ragged edge and in reality you won't know if and when your barrel starts blowing up bullets.
I shot in the same squad with a guy shooting a 22-250AI in 1:6.5". 95SMKs over 3000fps. I asked him if he ever had any issues with bullets coming apart. He confidently replied, Nope. And 1800rds on the barrel too. Three or four stages later, as the day heated up, he fired his first round on a stage. Easy target at 280yds or something. Flat out miss. Nobody saw splash or dirt. At that point I just stood directly behind him and watched out in front of his gun target line. He fired the second round and a grey puff appeared about 50yds out. I told him his bullet blew up. He didn't believe me but still couldn't figure out why he had a flat out miss and no dirt or splash. He never accepted it.
I think that's a pretty good parable about people who are confident in their 1:7" speed cartridges.
It's not a problem. Until it is.
But they do in the right barrel. And I have seen them.
Just because something is new to you, doesn't mean it's new to everyone else.
Push any bullet at stupid speeds they will break apart. AT 300k, they should not be. Hornady will.
Any thin jacketed bullet is susceptible to coming apart. Tight spots in the barrel, copper build up, that could cause jackets to be torn off. I have absolutely seen Berger bullets have this happen.
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