1:7" twist in 6.5mm...what's it for?

D

dms416

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Jan 12, 2014
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Central IL
#1
I'm seeing CORE has several 6.5mm blanks in 1:7 twist. (If you want LH twist, it's only in stock in 1:7)

I know the general mentality has been to err on the side of a faster twist especially if you go shorter (at least that was the old 308 logic), but is there any reason in a 6.5CM to go faster than 1:8 if I generally use 130gr Bergers? Does it change your opinion if I say I might go short (17-18")?

Thoughts?
 
#2
Supposedly berger is coming out with a 150 gr 6.5 bullet. That would be something you want faster twist for. Other than that just for really long solids maybe?

There are some old style really heavy 150-160 class hunter bullets, maybe for that but they are mainly round nose like the 6.5x55 has had moose hunting for decades and should be short enough to be stable in an 8 twist.
 
#3
The old 158's like you'd load for a swed stabilize in 1:8. I think sierra's 150smk is listed for 1:7 or 1:7.5. Some of the copper solids (too $$$ for me) may be 1:7 required.
 
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#7
On one of the pod cast, Frank talked about a short 260rem with a 7 twist and it help the BC. But i am not sure as to the context in which he was talking about the increase.
 
#13
DAVETOOLEY said:
Are you saying yes to faster twists?
Click to expand...

Im saying yes a 7 twist makes sense on .264 cal blanks if the chamber will be something on the higher end of case capacity to take advantage of the longer heavier bullets. Probably not optimal in a 6.5 creed although one could probably still find a few loads that may work. Hey, what do i know though?
 
#14
stello1001 said:
Im saying yes a 7 twist makes sense on .264 cal blanks if the chamber will be something on the higher end of case capacity to take advantage of the longer heavier bullets. Probably not optimal in a 6.5 creed although one could probably still find a few loads that may work. Hey, what do i know though?
Click to expand...
With higher velocities less twist is needed, even better at times. With extreme velocities rotational forces can and sometimes will destroy bullets. Until recently more has not always meant better.
Research Miller twist rule and go to Berger's website and play around with their twist rate calculator.
 
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#15
DAVETOOLEY said:
With higher velocities less twist is needed, even better at times. With extreme velocities rotational forces can and sometimes will destroy bullets. Until recently more has not always meant better.
Research Miller twist rule and go to Berger's website and play around with their twist rate calculator.
Click to expand...

I agree on the more velocity less aggressive twist. But maybe I didn't explain myself very well. So if we have a rifle chambered in 7.62x39, more than likely it won't be spitting out anything in the 200 plus grain category. If we have a 30 nosler, anything in the 200 plus might be good options. Because the 30 nosler has more case capacity and is able to launch longer heavier bullets, won't you prefer something with like a 9.5 twist versus maybe a 11.5 or 12 twist on the 7.62x39? I'm not trying to argue, I'm trying to see if we're both on the same page. If not, then I'm trying to learn.
 
#16
Basically we should be looking to optimize the twist rate for the intended bullet and expected velocity range....... longer bullets need faster twist but shoot them faster and less twist is required..... hitting the sweet spot will maximize the BC.

For instance, I'm trying the new 25 caliber 131gr blackjack bullets..... optimal twist in my Creedmoor is 1:7.25 while the exact same bullet in a 25-06 or other magnum offering would be better off with a 1:8twist tube.

I've done up a 6.5 Creedmoor with a 1:7 and shot the new Sierra 150gr bullets quite well a little more twist than needed but worked well.
 
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#17
It's a catch22 thing and I'm not talking solids for now.

I have a 9 twist Kreiger in 20 cal sitting in the corner because it tears up 55 grain Bergers, the long and heavy for caliber bullet I had planned to use from the start. For whatever reason 40vmax works with a mild load but 55's slowed down a lot more still wouldn't work. Chasing velocity, even though in 20x47 it was a medium load, I think the throat got torched early??? That's another thing, watch out when going to extremes, later on when the throat gets firecracked those long heavies might start grenading whereas they worked for a short while.

My 6.5 Saum Bartlein in 8.5 twist with 140 hybrid will blow up bullets at 3275 fps at the end of a longer string, At 3175 fps it won't. Certain bullets in certain barrels with normal twists can still have problems when pushed hard.

Plus the heaviest bullets for caliber might not be the most accurate in your rifle, another catch22.

So in a way launching those heavies slower in a faster twist, and in a normal sized cases, might be the way to go but you are really only gaining more energy at that juncture.

I'd be much more apt to pass on a 7 twist for heavy 6.5's and instead locate or order a 7.5 twist. Or maybe try a mild gain twist 8-7???. I'm kinda done trying ragged edge stuff though. I hate problems, I think I'd just rather hold for more wind.

Though the heavy for caliber bullets might work just fine in that super fast twist, but you won't know till you try???
 
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#18
steve123 said:
Though the heavy for caliber bullets might work just fine in that super fast twist, but you won't know till you try???
Click to expand...

Yeah, that's the only thing that would even be pertinent for me. I've pretty much flip-flopped from being largely 308 with 6.5 experimentation to the stark opposite. I'm starting to dip my toe into the sub-18.5" barrel area for 6.5 where if in 308, one would be using 1:10 or faster rates for 175 or 185's. I wasn't sure if the same applied to 6.5CM in the 130-140/142gr arena. I can understand saying a 1: 8.25-7.5 gain might make sense, but I don't even know if a gain would make much sense or be worth the trouble for this length/chambering/bullet weight.
 
#19
dms416 said:
Yeah, that's the only thing that would even be pertinent for me. I've pretty much flip-flopped from being largely 308 with 6.5 experimentation to the stark opposite. I'm starting to dip my toe into the sub-18.5" barrel area for 6.5 where if in 308, one would be using 1:10 or faster rates for 175 or 185's. I wasn't sure if the same applied to 6.5CM in the 130-140/142gr arena. I can understand saying a 1: 8.25-7.5 gain might make sense, but I don't even know if a gain would make much sense or be worth the trouble for this length/chambering/bullet weight.
Click to expand...

That gain twist might actually be a sweet spot. I remember once engaging in a thread where Frank and a few others, including myself, discussed GT barrels. It's got very useful insight. I'm gonna try and locate it for you. Especially since you wanna go with a relatively short barrel, you'll find the thread somewhat relevant as short barrels were discussed there if I recall correctly.
 
#20
I’m shooting 140 Hybrids in my 6.5x47 at 2725fps in a 1:7.2 Rock. Shoots great!
1CADEF11-3FC0-4885-911A-85611B318A8C.png
 
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#21
stello1001 said:
I agree on the more velocity less aggressive twist. But maybe I didn't explain myself very well. So if we have a rifle chambered in 7.62x39, more than likely it won't be spitting out anything in the 200 plus grain category. If we have a 30 nosler, anything in the 200 plus might be good options. Because the 30 nosler has more case capacity and is able to launch longer heavier bullets, won't you prefer something with like a 9.5 twist versus maybe a 11.5 or 12 twist on the 7.62x39? I'm not trying to argue, I'm trying to see if we're both on the same page. If not, then I'm trying to learn.
Click to expand...
I agree with that.
 
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#23
You can definitely overspin stuff. The trend for faster and faster twists can get you in trouble. I ordered a 6.5 PRC Proof research pre-fit but after waiting 12+ weeks for it, I realized the place I ordered through took the liberty of ordering me a 7 twist. They just assumed that would be good since the market is headed that way and Berger is supposedly coming out with a heavy 6.5mm one of these years. Long story short, I can get 140-143gr bullets up to 3130FPS safely, but they shoot like hot garbage at those speeds. The RPMs of the bullet is in the 320,000 range.I have heard from multiple sources, including bullet companies, to stay under 300,000 RPM. I had to back my load way down to 2940-2970 FPS for decent accuracy. Food for thought.
 
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#25
spelunk said:
You can definitely overspin stuff.
Click to expand...
Sometimes stuff that you think should fly right literally blows up 50 yards out in front.

I used to have a Model 70 match rifle in 260 Rem for highpower back in the early 2000s. Pretty normal 26" 1:8 Krieger. I settled on Lapua Scenar 123s for 200 and 300 yds and 139 Scenars for 600. Can't remember the exact load but it was in the mid 42s of H4350 for both.

Decided to try Hornady 95 VMax for 200 yds, mostly for lighter recoil in sitting rapid fire. At any sane velocity about half of them in a string would just evaporate about 50 - 75 yards downrange.
 
#27
I only shoot in the winter and my home range is 15' above sea level. My 8tw savage would not stablize the 150smk's I also have a negative DA nearly everyday I shoot. The 7tw on another creed shot the hell out of the smk's and he didn't get the eld fliers that I would get. If your above 1000' and 30 degrees you might be able to shoot the 8tw but it will cost you some points in bc with the 150 smk's in slow 6.5s. I shot my 12tw 308 this summer with the 215 berger@ 2595 and had first round hits @ 1100yds. @ 1700' near mom's house. Cut rifle barrels also will act like 1/2" faster twist in some cases as well.
 
#28
stello1001 said:
Im saying yes a 7 twist makes sense on .264 cal blanks if the chamber will be something on the higher end of case capacity to take advantage of the longer heavier bullets. Probably not optimal in a 6.5 creed although one could probably still find a few loads that may work. Hey, what do i know though?
Click to expand...
 
#29

I’m am in the midst of ordering a GAP in 6.5 CM and asked 1:7 vs 1:8. I’d take a 1:7.5. I was thinking bigger bullets like SMK. I will be in the States for a F2F after Shot. Probably a 25 or 26 tube. I wanted more than a 20-22 tube. Standing by.
 
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#33
cwinner said:
Basically we should be looking to optimize the twist rate for the intended bullet and expected velocity range....... longer bullets need faster twist but shoot them faster and less twist is required..... hitting the sweet spot will maximize the BC.

For instance, I'm trying the new 25 caliber 131gr blackjack bullets..... optimal twist in my Creedmoor is 1:7.25 while the exact same bullet in a 25-06 or other magnum offering would be better off with a 1:8twist tube.

I've done up a 6.5 Creedmoor with a 1:7 and shot the new Sierra 150gr bullets quite well a little more twist than needed but worked well.
Click to expand...
I picked up 200rnds of the 6.5 Sierra 150gr matchking. Do you think it would do ok through a bergara hmr b14 (1:8 24")??? thx
 
#34
I have a 1:7 18" Krieger barrel that shoots A Max 140s .25 MOA. I can get it to shoot the SMK 150s .5 MOA. I have 1000 of the SMK 150s and still trying to find the right load to get it where I want it. My luck I'll shoot the barrel out right after I find the right load, LOL. I have 700 of the 147s that I need to try in it also.
 
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#35
Shooter McGavin said:
I have a 1:7 18" Krieger barrel that shoots A Max 140s .25 MOA. I can get it to shoot the SMK 150s .5 MOA. I have 1000 of the SMK 150s and still trying to find the right load to get it where I want it. My luck I'll shoot the barrel out right after I find the right load, LOL. I have 700 of the 147s that I need to try in it also.
Click to expand...
Shooter McGavin said:
I have a 1:7 18" Krieger barrel that shoots A Max 140s .25 MOA. I can get it to shoot the SMK 150s .5 MOA. I have 1000 of the SMK 150s and still trying to find the right load to get it where I want it. My luck I'll shoot the barrel out right after I find the right load, LOL. I have 700 of the 147s that I need to try in it also.
Click to expand...
I called Bergara and they said... "We never tested above 143 and ONLY Hornady eldx on anything 6.5cm. So no we have no idea but you firing hand loads voids warranty".
 
#37
Shooter McGavin said:
I would imagine that you never tell them about the hand loads again. As far as the 1:8, SMK says on the box to use 1:7.5.
Click to expand...
Lucky I called from a unlisted number lol. Yep SMK says 1:7.5 but dealer said 1:8 should be fine with a heavy. But again, gotta test it. looking at Krieger's...
Ruger Precision Rifle6.5MM0.2560.2641-7.5.900@26"6.5 Creedmoor$575.00
 
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#38
For guys who's MV is below 2800 a 7 twist is okay

if you go too fast with the MV you'll destroy the bullets

it's not a heavy vs light thing, as people think, they are just trying to overspin them to transition better at transonic but it has limitations

I have a 7 twist 260, you just keep the speeds down, I have it in a 18" gun, with a good barrel you won't see much but noticeable drift at the edges

The gain twist is better, the Army went with w/ 7 Twist 260 and had to switch bullets because some can't handle it, they went 24" so the velocity was up and it wrecks jackets
 
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#39
lowlight said:
For guys who's MV is below 2800 a 7 twist is okay

if you go too fast with the MV you'll destroy the bullets

it's not a heavy vs light thing, as people think, they are just trying to overspin them to transition better at transonic but it has limitations

I have a 7 twist 260, you just keep the speeds down, I have it in a 18" gun, with a good barrel you won't see much but noticeable drift at the edges

The gain twist is better, the Army went with w/ 7 Twist 260 and had to switch bullets because some can't handle it, they went 24" so the velocity was up and it wrecks jackets
Click to expand...
Good info. Thx!!!!
 
#40
I've read reports about the Hornady 147 ELDMs blowing up but haven't experienced that yet. I'm not saying that it isn't going to happen to me but that I haven't experienced it yet.

Here's a target with an 8 shot group from my Krieger 1:7 RH twist barrel with factory 147 ELDM. The last time that I had it at 1,000 yards I was amazed.

8 shot 6-5 147 ELDM.jpg
 
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#42
Longshot231 said:
I've read reports about the Hornady 147 ELDMs blowing up but haven't experienced that yet. I'm not saying that it isn't going to happen to me but that I haven't experienced it yet.

Here's a target with an 8 shot group from my Krieger 1:7 RH twist barrel with factory 147 ELDM. The last time that I had it at 1,000 yards I was amazed.

View attachment 7545440
Click to expand...
that's tight!!! the damn dime won't get through without touching. Bravo!!!
 
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#46
Twist rate is one factor, it affects RPM. Other factors are velocity, barrel condition, rifling type.etc. But Hornady bullets are blowing up when others aren’t. They have now said that they do not recommend using their bullets at rpm greater than 290,000.
 
#47
I just received a 20” 7.0 twist +2 gas Krieger that John Scandale at Keystone Accuracy spun up for a 6.5 CM AR build. Only about 50 rounds down range so far in last two outings, with some intermittent cleaning to break in barrel. Extremely pleased with initial accuracy indications with 140 AMax and 41.5 H4350. This, in spite of my initial apprehension about 7 twist, with all of my other CM’s being 8 twist. Not had time to get to longer range yet, don’t anticipate an issue with older AMax, but we’ll see. Have thicker jacketed Scenars if an issue presents, and have inventory to support the option.
Following, to see other’s results. My initial velocity with 4350 was 2620ish, and expect barrel to speed up, but not going challenge RPM limitations noted above.
 
#48
From what I've seen, I believe barrel temperature is part of the equation. I'm running a 26" 7 twist 4 groove 6.5 PRC pushing 150 SMK @ 2940 and 153 Atip @ 2995. Accuracy is phenomenal with both, when things are running right. Able to blow either bullet up, just give me a hot summer day with enough round count. When the barrel gets heated, things start going poof. Have not had issues in fall/winter/spring times of the year where cooler ambient air temperatures kept my barrel temps down. The Sierra's seemed more resistant to blowing than the Atip. Currently, plan on trying some berger 153.5, but alas current supply/demand is making that difficult. Would love to have a long heavy monolithic to try.
 
#50
I have an essentially brand new 1:7 twist Hawkhill barrel on my old GAP Crusader (Defiance Rebel) action, currently collecting dust. The idea when I got it years ago was to spin as fast as possible to help with ELR shooting.

Now this thread has me wondering if I should get the barrel chopped down to ~16", and put a heavy flute (LRI "type X"?), to turn it into a hunting rifle. The current barrel is a 24" MTU, so in it's current configuration it's a heavy pig.

Could make for a fun project gun when I have some funds to do so :p
 
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