Subsonic 308 Winchester barrel twist rate?

[effendude]

I have a Tikka T3 chassis rifle that I shoot suppressed 308 Winchester rounds through. Running 160 grain Flex Tips at around 1050fps. Lots of fun and havoc on smaller varmints. I'd like to rebarrel with a slower twist to shoot heavier bullets, 180gr or heavier. My research shows most 300 Blackouts are 1-7" twist. Wondering what others are using? Bugholes has 1-8" barrels in stock.
Thanks,
Scott

 

[rijndael]

I'm using a 1:11 and 1:10 with 180gn Pro Hunter bullets. Subs out of my .308s are just for fun, it's not a dedicated barrel. I'm sure it's far from ideal, but it's working.

If I were going dedicated. I'd look at a blackout.

 

[effendude]

I have a lifetime supply of 308 brass. I'm not doing a blackout. And I don't want to lose a suppressor or tumble bullets.

 

[rijndael]

I'm at 1000'ish rounds of subs through my 2 guns. There haven't been any baffle strikes or signs of instability on the target.

 

[DirtySteve]

To be safe I would run the fastest twist possible. Then check a stabilizer calculator for peace of mind.

 

[BronzeArcher]

If in doubt, unscrew the suppressor and confirm stability on paper. My experience is that the stability calculator at the JBM ballistics site is right for subsonics in .308. It has never let me down and I have shot a lot of bullets in various twists and conditions.

JBM - Calculations - Stability

www.jbmballistics.com

 

[ebb]

7 or 8 twist

 

[Walt Krafft]

8 twist will be fine in a rifle length barrel. Pistol length 300 BLK can be as fast as 5 twist.

 

[1shot]

I'm running an 8 twist in a 16.25" bbl. No problems in several years, shooting 208 A max @ 1,050 fls.

Lloyd

 

[DaveTooley]

I like Hornady's 190 gr. sub bullet. It works fine in a 10 twist.

 

[Mr.Knowit all]

You will hear about folks shooting ridiculously slow twist with long bullets. 90% don't shoot subsonic past 300 meters with any repeatable accuracy. I had spoke with a guy that used 4 twist (that's 1 twist in 4 inches.) SMH..... and was trying to shoot subsonic out to a mile. He was testing a round for the military or a contractor I can't recall.... why the hell else would anybody want to do that? Are you starting to see the GENERAL trend? The further you want to shoot the faster you need your twist to me. I shoot a 1-7 twist on my 308 that I run 208s though and consistently (on nice days)make head shots at ~450 meters (LOTS of drop on those shots). 950 fps is the best speed for steal. I run mine closer to 1k fps. Mark White wrote a very good book on low-sig work. Good luck and that 8 twist should work for you.

 

[mgunderson]

Any more information on the book by Mark White?

 

[longbow]

My Bat switch barrel 30BR 1-11 lilja for cast bullet sub loads. Still playing with it four years now.I screw it on every Spring and keep dinking.1" groups at 100 yds... at higher velocity.The sub load is A tickler,but i'll get it yet.....Use powder coat bullets with the can.....

 

[WAMBO]

With 180"s you'd be fine with an 1-9" twist, 220's or heavier I'd want a 1-8" for subsonic.

 

[XTR]

… a guy that used 4 twist (that's 1 twist in 4 inches.) SMH.....

at some point that becomes threaded as opposed to rifled.

The “easy“ button for shooting that far subsonic is a 45-70 and a 535 gr bullet, don’t need bu5 about a 1:14.

 

[David Milisock]

I have a Tikka T3 chassis rifle that I shoot suppressed 308 Winchester rounds through. Running 160 grain Flex Tips at around 1050fps. Lots of fun and havoc on smaller varmints. I'd like to rebarrel with a slower twist to shoot heavier bullets, 180gr or heavier. My research shows most 300 Blackouts are 1-7" twist. Wondering what others are using? Bugholes has 1-8" barrels in stock.
Thanks,
Scott

If you want to shoot heavies I follow the lead of the Government barrels 1 in 7. They didn't pick it for no reason.

 

[284winner]

I have a Tikka T3 chassis rifle that I shoot suppressed 308 Winchester rounds through. Running 160 grain Flex Tips at around 1050fps. Lots of fun and havoc on smaller varmints. I'd like to rebarrel with a slower twist to shoot heavier bullets, 180gr or heavier. My research shows most 300 Blackouts are 1-7" twist. Wondering what others are using? Bugholes has 1-8" barrels in stock.
Thanks,
Scott

For 220 Berger's at 1200 fps in the 308 win assuming your around 1000 elevation, the 8 twist would be needed. The 9 twist gives unsatisfactory stability. Going to an 8 twist would be best. 200 on less would run fine in the 9 twist at similar speeds.

 

[Ray123]

I have a Tikka T3 chassis rifle that I shoot suppressed 308 Winchester rounds through. Running 160 grain Flex Tips at around 1050fps. Lots of fun and havoc on smaller varmints. I'd like to rebarrel with a slower twist to shoot heavier bullets, 180gr or heavier. My research shows most 300 Blackouts are 1-7" twist. Wondering what others are using? Bugholes has 1-8" barrels in stock.
Thanks,
Scott

I shot a bunch of 175 Serria MK subs out of various barrel lengths 18" to 30" and twist rates. 12 twist, 10 twist, 9 twist and 8 twist. They were accurate in all twist and lengths, had to add a half gr extra of Trail Boss with the 30" 8 twist barrel, with 10 to 10.5 gr of Trail Boss depending on barrel length. It did not operate the AR 10 action... but I didn't expect it to...velocities were right at 1050 fps.Heavier bullets I'd lean to faster twist rates as bullet length goes up. No suppressor used