Short 308win barrel twist rate for subs/why no fast twist 308 barrels?

beetroot · Oct 31, 2024

Been looking at getting a short 308 barrel for a little while with the hopes of running subsonics for plinking/fun/limited hunting, but still shoot supers.
Looking at posts on here and playing with the Berger stability calculator, it seems like a standard 1:10/11/12 twist barrel are capable of handling subsonics, the 1:10 being the best candidate but all able to do it if you choose the right projectile.

However, I can't help but wonder why 1:8 twist barrels for 308win aren't a thing, especially shorter barrels.
1:8 is more or less than standard twist of 300 Norma, so there is obviously no risk in a short barrel 308 over spinning bullets.
Running the numbers on a 110gr bullets @ 3000fps in a 1:8, the RPMs are 270,000 which is getting up there but still comfortably under the 300k magic number.

If I'm going to get a 16-1" barrel spun up and want the most versatile twist possible, what should I go for? Stick with a more standard 1:10, or go faster to a 8 or 9 twist?
I'm dream (probably a pipe dream) would be able to comfortably run subsonics, 125gr TMKs and 168-175gr SMK/TMKs.

sparky702 · Oct 31, 2024

beetroot said:
Been looking at getting a short 308 barrel for a little while with the hopes of running subsonics for plinking/fun/limited hunting, but still shoot supers.
Looking at posts on here and playing with the Berger stability calculator, it seems like a standard 1:10/11/12 twist barrel are capable of handling subsonics, the 1:10 being the best candidate but all able to do it if you choose the right projectile.

However, I can't help but wonder why 1:8 twist barrels for 308win aren't a thing, especially shorter barrels.
1:8 is more or less than standard twist of 300 Norma, so there is obviously no risk in a short barrel 308 over spinning bullets.
Running the numbers on a 110gr bullets @ 3000fps in a 1:8, the RPMs are 270,000 which is getting up there but still comfortably under the 300k magic number.

If I'm going to get a 16-1" barrel spun up and want the most versatile twist possible, what should I go for? Stick with a more standard 1:10, or go faster to a 8 or 9 twist?
I'm dream (probably a pipe dream) would be able to comfortably run subsonics, 125gr TMKs and 168-175gr SMK/TMKs.

I run some winchester 168 grain open tip's subsonic in my Remington 700 308 20 inch barrel 1/10 twist and they flew pretty good I zeroed at 50 yds and was dinging a reduced size target 12 " x 20 " at 200 yds pretty easy . It's like a mortar barrage . I am fixing to try some 190 grain sub-x hornady's I have a couple hundred bullets a can of trail boss and plenty of primers . My initial intent was to load a bunch of sub's for my 300 blackout rifles but as usual somebody on here commented on loading the 190's in a 308 so that will happen some time in the near future .

Overwatch260 · Oct 31, 2024

Years ago I ran a 16" 10 twist .308 with up to 208 gr AMAX & 220 gr round nose subsonic loads with Trailboss powder, they did great in that twist rate. I personally think you'd be fine with a regular 1:10 for what you're looking to do @beetroot .

FuhQ · Nov 1, 2024

If going shorty, go ahead and get a 1:7 if you have the option. Better to be slightly over-stable than slightly under… Especially if you want to run 210-240gr subs.

beetroot · Nov 1, 2024

Overwatch260 said:
Years ago I ran a 16" 10 twist .308 with up to 208 gr AMAX & 220 gr round nose subsonic loads with Trailboss powder, they did great in that twist rate. I personally think you'd be fine with a regular 1:10 for what you're looking to do @beetroot .

Thanks. 208gr Amax stabilizing is a good sign.

roostercogburn98 · Nov 1, 2024

I got an 18 inch 1-11.25 coming to me soon I hope. I’m hoping to do a wide range of bullet weights to start with. Not sure what I’ll settle with weight wise though.

Scopes · Nov 2, 2024

I have 16" 8 twist 308 win. It shoots 175 and 185 around 2400 fps. Accuracy is excellent.

beetroot · Nov 2, 2024

Scopes said:
I have 16" 8 twist 308 win. It shoots 175 and 185 around 2400 fps. Accuracy is excellent.

Factory or did you get it spun?

2400fps is pretty respectable from a 16" bbl.

beetroot · Nov 2, 2024

FuhQ said:
If going shorty, go ahead and get a 1:7 if you have the option. Better to be slightly over-stable than slightly under… Especially if you want to run 210-240gr subs.

I'm not sure I'd go for a 1:7. I'm sure it'd be perfect for 150gr+ and subs, but for the lighter bullets it might be a little too fast.

epeet · Nov 2, 2024

I had a 1:8 with thousands of rounds on it. I think you start to be asking a lot of .308 to have it perform well with subs. I know that Swiss P makes some .308 subs. But I think that internal case volume is an issue for consistent muzzle velocity. I won't buy another 1:8 because the spin drift gets pretty out of control as you start walking the rounds out.

beetroot · Nov 2, 2024

epeet said:
I had a 1:8 with thousands of rounds on it. I think you start to be asking a lot of .308 to have it perform well with subs. I know that Swiss P makes some .308 subs. But I think that internal case volume is an issue for consistent muzzle velocity. I won't buy another 1:8 because the spin drift gets pretty out of control as you start walking the rounds out.

Yeah there's a good reason why Trailboss is the go to powder for 308 subs.

Looks like some pistol powders will work and even something like H4895 is meant to be ok at low fill, but TB is really the only reliably good option.

FuhQ · Nov 2, 2024

epeet said:
I had a 1:8 with thousands of rounds on it. I think you start to be asking a lot of .308 to have it perform well with subs. I know that Swiss P makes some .308 subs. But I think that internal case volume is an issue for consistent muzzle velocity. I won't buy another 1:8 because the spin drift gets pretty out of control as you start walking the rounds out.

Use trail boss and your powder problems disappear. In thousands of subs I’ve made, never a single hangfire, dud, or squib.

Also, my 168gr sub load shoots an average between 1/2-1 MOA @ 100 with a very ES & SD, from my factory 5R Milspec with an 11.25” twist barrel. Subs can be extremely accurate, provided the gun itself is, and you actually know what you’re doing loading them and using the right components for the job.

Scopes · Nov 2, 2024

beetroot said:
Factory or did you get it spun?

2400fps is pretty respectable from a 16" bbl.

Factory Desert tech barrel.

45-90 · Nov 2, 2024

I run 308s in 12, 11.35, 10, 9, & 8, 16" to 30" barrels, auto, bolt, SA and LA.
I prefer 9 and 8 twists for most uses.
The 8 twist 30" barrel is very accurate with supers and subs 130 gr to 230 gr Atip. 250 gr works too but needs a longer throat for real performance, in supers, but have not tried it with subs.

I have shot nice groups with 308 subs with 175 gr match bullets, with most of the above twists.
Even used shotgun primers in 308 subs, in modified cases.

beetroot · Nov 2, 2024

45-90 said:
I run 308s in 12, 11.35, 10, 9, & 8, 16" to 30" barrels, auto, bolt, SA and LA.
I prefer 9 and 8 twists for most uses.
The 8 twist 30" barrel is very accurate with supers and subs 130 gr to 230 gr Atip. 250 gr works too but needs a longer throat for real performance, in supers, but have not tried it with subs.

I have shot nice groups with 308 subs with 175 gr match bullets, with most of the above twists.
Even used shotgun primers in 308 subs, in modified cases.

How does the 1:12 handle subs? Do you have to be careful with what projectiles you use?

Seems like 175 and 178 are pretty easy to get a sub load for. Good for targets but not what you'd choose for hunting.

D̷e̷v̷i̷l̷D̷o̷c̷A̷Z̷ · Nov 2, 2024

Study this a while.

https://hodgdonpowderco.com/wp-content/uploads/2023/04/subsonic-data-final-1.pdf

Combine this with your studies

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

Alternatively send me $200 and I’ll get on the phone w you for an hour.

FuhQ · Nov 2, 2024

beetroot said:
How does the 1:12 handle subs? Do you have to be careful with what projectiles you use?

Seems like 175 and 178 are pretty easy to get a sub load for. Good for targets but not what you'd choose for hunting.

Yes, you will have to run 150-168gr subs in anything slower than a 1:10 twist.

My 16" Christensen MPR .308 Win (1:10) loves Berger 210 VLD/Nosler 210RDF subs. Shoots sub-MOA with them @ 100, and have taken them out to 200 & 300 with no issues, and consistent accuracy and precision. You really just have to kind of play with it, and figure out what your gun likes best and adjust from there.

My R700 5R Milspec 22" 11.25 twist keyholes 210's @ 100 bad. Like completely sideways impacts if it even hits the damn target. But 168gr subs, it stacks them in there, just like it does with 168 supers.

beetroot · Nov 2, 2024

FuhQ said:
Yes, you will have to run 150-168gr subs in anything slower than a 1:10 twist.

My 16" Christensen MPR .308 Win (1:10) loves Berger 210 VLD/Nosler 210RDF subs. Shoots sub-MOA with them @ 100, and have taken them out to 200 & 300 with no issues, and consistent accuracy and precision. You really just have to kind of play with it, and figure out what your gun likes best and adjust from there.

My R700 5R Milspec 22" 11.25 twist keyholes 210's @ 100 bad. Like completely sideways impacts if it even hits the damn target. But 168gr subs, it stacks them in there, just like it does with 168 supers.

Cheers.

Based on the feedback it would seem my initial assumption that fast twist 308 barrels probably should be more common, especially on shorter barrels but the cartridge seems to be very forgiving on twist rates so the "standard" 1:10 is good enough.

If I end up getting a barrel spun up I see no reason not to go for a 1:8. However I might have a lead on a well priced prefit/used barrel and I'm guessing itll be a 1:12 twist, hence the questions on the slower twists.

FuhQ · Nov 2, 2024

beetroot said:
Cheers.

Based on the feedback it would seem my initial assumption that fast twist 308 barrels probably should be more common, especially on shorter barrels but the cartridge seems to be very forgiving on twist rates so the "standard" 1:10 is good enough.

If I end up getting a barrel spun up I see no reason not to go for a 1:8. However I might have a lead on a well priced prefit/used barrel and I'm guessing itll be a 1:12 twist, hence the questions on the slower twists.

There's a reason .300 BLK is a 1:7 twist as standard twist rate...Slow .30 caliber subs with shorter barrels produced better ballistics with more RPM's to spin the slow-moving heavy bullets (same principle for supers, too). That's why if someone is going to build a .308 Win that's 16" or shorter, and wants to mainly shoot subs with the ability to shoots supers without overspinning them, I'd say 1:8 to 1:9 twist, but if you want to shoot 210-220gr supers, as well, then a 1:7 or 1:8 would be best for stabilization.

Charger442 · Nov 2, 2024

epeet said:
I had a 1:8 with thousands of rounds on it. I think you start to be asking a lot of .308 to have it perform well with subs. I know that Swiss P makes some .308 subs. But I think that internal case volume is an issue for consistent muzzle velocity. I won't buy another 1:8 because the spin drift gets pretty out of control as you start walking the rounds out.

this was not my experience. 1:8 twist taking 175 grains out to 1000 and beyond. really accurate especially made by Mark Gordon..

beetroot said:
Cheers.

Based on the feedback it would seem my initial assumption that fast twist 308 barrels probably should be more common, especially on shorter barrels but the cartridge seems to be very forgiving on twist rates so the "standard" 1:10 is good enough.

If I end up getting a barrel spun up I see no reason not to go for a 1:8. However I might have a lead on a well priced prefit/used barrel and I'm guessing itll be a 1:12 twist, hence the questions on the slower twists.

i spoke with a smith at Douglas barrels probably 15 years ago when i built my first custom on an FN. he said there's no reason to recommend anything slower than a 1-10 for 308 as it covers everything so well.

that being said, i love my 1-8 twist 308 and it hammers with the heavier bullets but i don't shoot subs with it because what's the point? i have other calibers that do better for that

45-90 · Nov 2, 2024

beetroot said:
How does the 1:12 handle subs? Do you have to be careful with what projectiles you use?

Seems like 175 and 178 are pretty easy to get a sub load for. Good for targets but not what you'd choose for hunting.

I loaded up some 175 gr with Trail Boss and took them out th the range.
Along with a variety of 308s. The 175 SMK shoots well in 12, 10, 9 & 8 for universal sub work.
I did plan on hunting with them or any sub, except on small game.
But I shoot the expanding bullets for fun in many different calibers from the 300 blk to 510 Whisper.

You can purchase store bought 308 sub ammo with 180 gr REX expanding bullets around $45 per 20.
Or go to Maker and just by 50 bullets for a similar price and load them yourself.
The Ammo company recommends a 1-10 twist, but testimonials say they got away with 1-12.
I'd stick with the 1-10 twist recommended by the ammo maker for 16" to 20" barrels.
The twist rate and sub performance is regulated by the bullet length and the physical changes made by the maker to get them expand usually in gel at the sub speeds and twist rates recommended.
They work in a narrow window, for velocity and twist rate design.
Example one designed for 6.5 twist will blow the copper petals off the bullet before it reaches the target in a 3 twist barrel.
A 3 twist bullet won't open properly in a 6.5 twist barrel.
That can be changed and adjusted with machine tools.
Bottom line try the 180 Maker in your short barrel 16" to 20" recommend by the ammo maker in your 10 twist ...it does not operate autos.
Or buy some 180s from Maker, run the sub speed to the 1100 fps mark to open the bullet if you try the 12 twist, 1000 to 900 fps for 10 and 9 twists. Experiment to see what works in your barrel.

beetroot · Nov 2, 2024

Charger442 said:
i spoke with a smith at Douglas barrels probably 15 years ago when i built my first custom on an FN. he said there's no reason to recommend anything slower than a 1-10 for 308 as it covers everything so well.

There really does not seem to be any good reason to go slower than 1:10, if 1:8 is fairly standard for 300 Norma and 300 PRC then a 1:12 308 in 2024 makes little sense.

My hypothesis is that just like 223, 243, 22-250 all used to be commonly found in 12-14 twist barrels but are now all 1:9 or faster, the 1:12 308 twist is just a hangover from yesteryear, and has only stuck around because 308 is so common.
Almost no one would build a 22 Creedmoor on a 1:14 twist these days (common twist for 22-250) so doesn't seem to be any good reason to not apply the same logic to 308.

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Short 308win barrel twist rate for subs/why no fast twist 308 barrels?

Which twist for short barrel 308 running subs and supers (basically like a 300blk)

1:7

1:8

1:9

1:10

1:11

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