PROOF 8.4 twist .284 barrels?

[Glassaholic]

I may need to get a new barrel soon for my SAUM and was looking at the latest PROOF is offering and saw they offer 1:9, 1:8.4 and 1:8. Maybe I missed a memo or something but 1:8.4 seems a little odd in a world of whole numbers, has the 8.4 twist been proven to show inherent better accuracy vs. other twist rates with heavy bullets or can anyone shed some light on why 8.4? Thanks

 

[DAVETOOLEY]

Proof's rifling machines are gear gear driven. That is the part that controls the rifling head. That means 1:8.4 is as close as they can get to 1:8.5

 

[Glassaholic]

Thank you Dave, the odd thing is that in .243 and .264 they offer 7.5 twist, but .284 they offer 8.4 and in 308 and 338 offer 9.4. I know there have been some advancements in rifling but wasn't sure if there was something magical about 8.4.

https://www.proofresearch.com/the-products/barrels/bolt-action-cf-barrels/

 

[DAVETOOLEY]

There is very little magical about twist rates. You need enough to get the job done and a well designed bullet.

 

[Glassaholic]

There is very little magical about twist rates. You need enough to get the job done and a well designed bullet.

Okay, so you see little difference between 1:8 and 1:8.4 because that's what I saw and was curious why they offered both.

 

[DAVETOOLEY]

Any change +/- .5 will get lost in the noise unless you are at the extremes. Then too slow and bullets go sideways. Too fast and bullets either don't shoot well or go poof.

 

[bjay]

Any change +/- .5 will get lost in the noise unless you are at the extremes. Then too slow and bullets go sideways. Too fast and bullets either don't shoot well or go poof.

I agree with dave
I built my first hunting 300nm improved with 1.9:4 26" and i cant get it shoot with 212 eld-x and 215hyb..i called proof and told them im wasting too much powder bullets just get a concistent .5 moa..
Monte from proof said send him the barrel and he will diagnose it but for the main time he's shipping me another barrel.he offer me any length with twist 1/9 ,1/9.4 or 1/10 i picked 1/10 24" and that thing shoots laser with 215 BUT its diff reamer..bigger neck and longer freebore..im not sure which had fixed the issue

 

[5RWill]

I always default to nearly the fastest offering, especially in magnums, given the extra powder capacity i'm going to want to take full advantage. Pretty much the reason i went with 1:8 for my 284 blank. I want to run 180s at 3000fps and might try the 195s if the Sherman Short can get them up to 2900fps.

 

[bjay]

I always default to nearly the fastest offering, especially in magnums, given the extra powder capacity i'm going to want to take full advantage. Pretty much the reason i went with 1:8 for my 284 blank. I want to run 180s at 3000fps and might try the 195s if the Sherman Short can get them up to 2900fps.

What cartridge?

 

[5RWill]

What cartridge?

7 sherman short mag. Rich got 2955fps with 195s out of a 26" tube. My main goal is 180gr ELD-M at 3000fps. Which i think it's attainable with RL26.

 

[bjay]

7 sherman short mag. Rich got 2955fps with 195s out of a 26" tube. My main goal is 180gr ELD-M at 3000fps. Which i think it's attainable with RL26.

Thats fast for let say 7saum improved?
I had saum with 28.5" i could only gt 2950 with rl25 180hybrids

 

[Glassaholic]

Thats fast for let say 7saum improved?
I had saum with 28.5" i could only gt 2950 with rl25 180hybrids

Similar to you bjay, 2958 with RL25 and 180 Hybrids out of my 7 SAUM

 

[5RWill]

Thats fast for let say 7saum improved?
I had saum with 28.5" i could only gt 2950 with rl25 180hybrids

Essentially yes. No doubt but that's pushing with RL26 also. But he was getting 12+ firings also. While i never used 25 i've yet to see a powder outpace 26 in the SAUM casing granted i've mainly looked back and forth between H1000 and RL26 because both are temp stable. But 26 is pretty stout gives me a 100fps over H1000 at a lower charge with our 6.5 SAUM.

3200fps for 168s, 3100fps for 175s, 3070fps for 180s, and 2955fps for 195s. Were Rich's numbers. I'll see if i can dig up the charge.

 

[Glassaholic]

Any change +/- .5 will get lost in the noise unless you are at the extremes. Then too slow and bullets go sideways. Too fast and bullets either don't shoot well or go poof.

Thank you Dave. I prefer to shoot the heavies out of my 7 SAUM, so would you suggest I just stick with 1:8 and not worry about the 1:8.4. By the way, my current barrel is a 1:9 and does a decent job with the 180's but I remember Bryan Litz mentioning that with some of the long bullets they may lose stabilization at distance with faster twist rates and are better stabilized with slower twist rates.

 

[Glassaholic]

Essentially yes. No doubt but that's pushing with RL26 also. But he was getting 12+ firings also. While i never used 25 i've yet to see a powder outpace 26 in the SAUM casing granted i've mainly looked back and forth between H1000 and RL26 because both are temp stable. But 26 is pretty stout gives me a 100fps over H1000 at a lower charge with our 6.5 SAUM.

3200fps for 168s, 3100fps for 175s, 3070fps for 180s, and 2955fps for 195s. Were Rich's numbers. I'll see if i can dig up the charge.

Will, I haven't seen RL26 in the wild here in Colorado yet so haven't had a chance to play with it, but your numbers over RL25 are impressive! I also use H1000 which shows improvement over RL25 for my 175gr Hornady ELD-X hunting load, but 100fps is a lot, and I'm assuming you've seen no pressure warnings in LD?

 

[5RWill]

Will, I haven't seen RL26 in the wild here in Colorado yet so haven't had a chance to play with it, but your numbers over RL25 are impressive! I also use H1000 which shows improvement over RL25 for my 175gr Hornady ELD-X hunting load, but 100fps is a lot, and I'm assuming you've seen no pressure warnings in LD?

I think i'm creeping towards it, though my max loads down here tend to be lower than most people. I'll have to check my load data when i get home but 60gr of h1000 gave us 2935fps avg with 140gr Elite Hunters. 60gr of RL26 is giving me 3059fps avg with 143gr ELD-X which has a longer bearing surface to my knowledge. Now you could argue that the barrel has speed up but it only has 120rds on it. Simply put i was having to push hard with H1000 to achieve what i wanted or expected out of a 23" 6.5 SAUM.

Here was my data with RL26 this was i believe in 50F or so i'll have to look at my log. Then the second pic is in nearly 90F later on. Was trying to test how temp stable it was. I just switched to regular large rifle primers also.
58.5gr - 3007fps average SD - 17.9
59.0gr - 3011fps average SD - 15.5
59.5gr - 3029fps average SD - 4.2
60.0gr - 3059fps average SD - 4.2

 

[DAVETOOLEY]

Thank you Dave. I prefer to shoot the heavies out of my 7 SAUM, so would you suggest I just stick with 1:8 and not worry about the 1:8.4. By the way, my current barrel is a 1:9 and does a decent job with the 180's but I remember Bryan Litz mentioning that with some of the long bullets they may lose stabilization at distance with faster twist rates and are better stabilized with slower twist rates.

You won't see any difference between the two.