AI .308 Twist Rate vs Year of the Bullet

[03psd]

I just got done reading LL Year of the Bullet article. Its a great article. Most of it is way over my skill level but one thing that did resonate and stick with me was his statement about .308 twist rates:

One of the success stories of the Ruger Precision Rifle was the twist rate. Ruger recognized that most factory rifles were giving you the wrong twist rate to truly shoot effectively at long distance. For the 308 the rule was to use a 1-12 and assume the shooter will use the crappy 168gr bullet. That is one of the worst choices for shooting Long Range you can make. We have progressed so far past the design of the 168 is comical to even read about it. I get it, the 168 is a cheap solution for Long Range shooting, but trust me, Long Range Shooting is not cheap so stop taking this shortcut. To answer your question, the 175 will work in a 1-12, but part of the success of the RPR is the 1-10 twist rate. Companies reading this, please retire the 1-12. Minimum today should be the 1-11.25.

Here I am about to drop $5k on an AIAT and I read this and yup, you guessed it, all AI .308 rifles come with a 12 twist barrel. I hadnt planned on the factory AI barrel being a throw away so now I am second guessing my decision. I fully understand that there are better caliber choices for LR and I do plan on getting a 6.5 barrel as well but I hadnt seen anyone communicate such definative and unflattering thoughts on the SMKs(presumably) or the 12 twist barrel. Please understand this is not a criticism of LL or the article. To the contrary, my respect for his knowledge and insight has me concerned with my choice and quite honestly, has me wondering why AI continues to use a 1:12 twist on their rifles if the shooting world has moved so far beyond them.

 

[Aaron47pb]

.... has me wondering why AI continues to use a 1:12 twist on their rifles if the shooting world has moved so far beyond them.

Because they still work... 175s shoot great out of my LW 1:12 twist. I haven't shot them personally, but I know a couple people who shoot 185 jugs out of them with great results.

 

[FunwithaGun]

Respectfully, why start with a .308? Having owned many,
a couple 6.5's and a couple 6mm's of different varieties, I wouldn't even think of choosing It as a first or primary caliber. I say this as someone who really likes the .308, it's just that the .308 is to a .260 what a 168 match king is to a 200 gr. Berger.

Just my opinion,

 

[FunwithaGun]

Also fwiw, I learned to shoot and reload well with a .308 and will probably always own one, so no hating here

 

[03psd]

Respectfully, why start with a .308? Having owned many,
a couple 6.5's and a couple 6mm's of different varieties, I wouldn't even think of choosing It as a first or primary caliber. I say this as someone who really likes the .308, it's just that the .308 is to a .260 what a 168 match king is to a 200 gr. Berger.

Just my opinion,

Fun - Its a fair question and no disrespect taken. Honestly, it comes down to the fact that I like the AI platform. The chassis works well for me. I have a custom .308 in a AICS chassis that I enjoy but I plan to rebarrel it to a fast twist .223 when I get a new rifle. All short action AI appear to me to come in .308. There are other barrels available but I am unaware they will sell you one with a different caliber from the factory. If they will, please tell me. I wont drop .308 all together because like you I enjoy the caliber. I planned on having the factory .308 barrel cut to ~18" and threaded and pick up either a AI or aftermarket Gladous or Toomey 6.5CM barrel. The user changeable barrels on the AIAT is very slick and definetly a plus in my opinion.

 

[sierracharlie338]

I have shot 10 and 11.25 twists with great results for the 175-178. I personally have never shot a 12 twist so I won't lend much help there. What I can tell you is if you have reservations about the nonnegotiable twist rate I would wait and research a little more before putting that much money into something you may mindfuck yourself on before it even hits your door.

 

[L.R.Novice]

I have the 1:12 20" factory AIAT barrel and use 175 smks. It may not be as stabilized as it should be but I get great accuracy printing groups at 100-200 yards and banging steel out to 700. I also see AI takeoff barrels selling quickly online so there is a market if you want to sell it.

 

[Supersubes]

Mile high or euro will sell you one in the 6.5 of your choice. Mile high has an up charge for that, not sure about euro. It would be cheaper to buy it .308 and buy a spare 6.5 barrel. Then sell of the .308.

12 twist is fine. It will stabilize all the traditional bullets, but would struggle with the newest heavies people have been chilucking out of their .308's(i think). I'm of the opinion that there is no use for the .308 when you could have a creedmoor.

 

[Supersubes]

I have the 1:12 20" factory AIAT barrel and use 175 smks. It may not be as stabilized as it should be but I get great accuracy printing groups at 100-200 yards and banging steel out to 700. I also see AI takeoff barrels selling quickly online so there is a market if you want to sell it.

The 175 in a 12 twist at 2625 fps has a sg of 1.5 at 30.50 pressure in zero degree temps. In .308 effective ranges, youre golden.

 

[308220]

A 155 TMK screaming along at 2900-2950+ fps is nothing to sneeze at. A 12 twist handles that easily. Not everybody lobs a mortar out of their 308. But for shorter barrels wanting to go long range, yeah, a 10-11 twist is needed.

 

[308220]

I'm of the opinion that there is no use for the .308 when you could have a creedmoor.

For what? Competition? Hunting?

 

[digrazir]

A 12 twist 308 works just fine...155, 168 and 175 grain bullets shoot lights out in my AI AT. If I feel the need to shoot heavy 30 cal bullets I would get a 30-06 or a 300 win mag. Ray

 

[viper42]

There are obvious ballistic advantages to the 6.5 CM, but when it really boils down to it the guy who knows his stick and reads the wind will win the day.

 

[Ren]

Like others have already stated nothing wrong with a 1/12. I have shot 190 smk's out of 3 different 1/12 twist barrels. 2 FN spr's and an AI. Crushes steel like a freight train at distance... 6 to 800 yards.

 

[jwood1284]

AIAT with factory 20". 175gr Nosler CC at 2620. No problems here.

 

[shamir]

I think MileHigh will sell you an AI AT with a custom .308 barrel rather than the factory 1-12. Have you checked with them ?

 

[dannySH]

I have two .308 rifles, both with 1/11 twist rates and both love heavy bullets like 175 -180 grains better than 155 - 168 grains

Sent from my SM-T810 using Tapatalk

 

[Supersubes]

For what? Competition? Hunting?

Yes.

 

[Laseredge]

My stock 1/12 20" .308 AIAT barrel shoots 175 gr. SMKs and 185 gr. Juggs into .5moa at 100, and tags 1.5moa steel at 1k, no problem. The only variable is that this is shooting between 5000 and 7000 feet above sea level.

Mile High will sell you an AIAT with any barrel you want, it will just cost you more. They most likely will not give you much trade-in for the stock 1/12 barrel. So I say keep it and shoot it. If it does not work for you sell it. You will end up with other barrels anyway.

 

[phlegm]

My AX308 shoots 208 A-Maxs just fine. I've settled on 175s for everyday shooting, so I don't think I'm limited by the twist rate.

 

[03psd]

My AX308 shoots 208 A-Maxs just fine. I've settled on 175s for everyday shooting, so I don't think I'm limited by the twist rate.

your AX308 comes with a 1:10 twist so it should do better with the heavies. The AT comes with a 1:12 twist. Why? I have no idea. Its pretty dumb. The barrels are interchangeable but I not sure any retailer is going to be willing to swap barrels off 2 new guns in their inventory to satisfy a customer. If there is, please let me know and I will buy it from them all other things being equal!

 

[308220]

Yes.

Id rather have a 308 for hunting inside 500-600 yards, personally. The velocity and bullet performance (mushroom) just works. Some of the worst entry/exit wounds Ive ever saw came from a 308. Its nothing for a 308 to blow plum through an elk standing broadside at 500 yards. So I dont think sectional density is a major concern. Heavier bullet. Bigger hole. More power at most hunting distances. 308, please. And out to 500-600, theyre all pretty close in drop/drift.

But, everybody has their own flavor.

 

[Supersubes]

Id rather have a 308 for hunting inside 500-600 yards, personally. The velocity and bullet performance (mushroom) just works. Some of the worst entry/exit wounds Ive ever saw came from a 308. Its nothing for a 308 to blow plum through an elk standing broadside at 500 yards. So I dont think sectional density is a major concern. Heavier bullet. Bigger hole. More power at most hunting distances. 308, please. And out to 500-600, theyre all pretty close in drop/drift.

But, everybody has their own flavor.

I think the energy/penetration is splitting hairs for each of them. In drop and drift though, is not. The 6.5 is outperforming the .308 soundly with everage loads. Then one has to consider priorities. What is the OP buying an AT for? I doubt hunting is the first priority. Given a choice for a LR precision gun, the creedmoor seems the obvous one. Like you said though, to each their own.

 

[308220]

I think the energy/penetration is splitting hairs for each of them. In drop and drift though, is not. The 6.5 is outperforming the .308 soundly with everage loads. Then one has to consider priorities. What is the OP buying an AT for? I doubt hunting is the first priority. Given a choice for a LR precision gun, the creedmoor seems the obvous one. Like you said though, to each their own.

Who knows, people hunt with every platform under the sun now days. Yeah, the 6.5 CM outperforms the 308 at longer ranges. But at 500 yards for example, they are near identical.100 yard zero. 500 yards stats.

Exhibit A

178 Eld X .534 BC
2650 fps (average)
1428 ft lbs
Drop 3.2 mils
Drift 1 mil

Exhibit B

140 ELD .610 BC
2775 fps (average)
1362 fl lbs
Drop 2.7 mils
Drift .8 mils


So not really "soundly" until you stretch it out a bit further. My post is at defending the 308 as a hunting round. Not as a competitive competition round.

 

[03psd]

My stock 1/12 20" .308 AIAT barrel shoots 175 gr. SMKs and 185 gr. Juggs into .5moa at 100, and tags 1.5moa steel at 1k, no problem. The only variable is that this is shooting between 5000 and 7000 feet above sea level.

Mile High will sell you an AIAT with any barrel you want, it will just cost you more. They most likely will not give you much trade-in for the stock 1/12 barrel. So I say keep it and shoot it. If it does not work for you sell it. You will end up with other barrels anyway.

You are correct and I just did! Ordered an AIAT with a 1:10 Bartlein. Its a $400 upcharge from the Lothar Walther 1:12. Not chump change by any means but clearly a significant upgrade and its exactly what I wanted. They cut it to my length and threaded it as well for the $400.

 

[Devildog]

Play around with this twist rate calculator maybe it'll help if you know what you plan to shoot. http://www.bergerbullets.com/twist-rate-calculator/
By the way I'm a 308 guy, it's very seldom I get the chance to shoot past 500 yards so I don't see a lot of advantage to getting a barrel burner unless I could shoot extended distances were there are better choices then 30 cal. Also my 308 & 300 wsm both have 1-11 twist barrels.

 

[ballisticdaddy]

I believe it all comes down to intended use for the .308 cartridge. I have an RPR in 6.5CM and shoot it in club matches frequently but also have a REM 700 Mil-Spec 5R with 11.25 twist rate. If the wind is not howling the .308 (175 SMK using 35 MOA drop) will be very competitive with the 6.5CM (140 VLD using 28.5 MOA drop) out to 1,000 yards. But if the wind kicks up its a whole different ballgame. The only advantage to the 1:10 twist is if you plan to load the heavy projectiles +185.

 

[Ren]

For all you guys that hate your AI 1:12 twist rate barrels, ill pm you my address for proper disposal.

 

[Nik H]

I just got done reading LL Year of the Bullet article. Its a great article. Most of it is way over my skill level but one thing that did resonate and stick with me was his statement about .308 twist rates:

One of the success stories of the Ruger Precision Rifle was the twist rate. Ruger recognized that most factory rifles were giving you the wrong twist rate to truly shoot effectively at long distance. For the 308 the rule was to use a 1-12 and assume the shooter will use the crappy 168gr bullet. That is one of the worst choices for shooting Long Range you can make. We have progressed so far past the design of the 168 is comical to even read about it. I get it, the 168 is a cheap solution for Long Range shooting, but trust me, Long Range Shooting is not cheap so stop taking this shortcut. To answer your question, the 175 will work in a 1-12, but part of the success of the RPR is the 1-10 twist rate. Companies reading this, please retire the 1-12. Minimum today should be the 1-11.25.

Here I am about to drop $5k on an AIAT and I read this and yup, you guessed it, all AI .308 rifles come with a 12 twist barrel. I hadnt planned on the factory AI barrel being a throw away so now I am second guessing my decision. I fully understand that there are better caliber choices for LR and I do plan on getting a 6.5 barrel as well but I hadnt seen anyone communicate such definative and unflattering thoughts on the SMKs(presumably) or the 12 twist barrel. Please understand this is not a criticism of LL or the article. To the contrary, my respect for his knowledge and insight has me concerned with my choice and quite honestly, has me wondering why AI continues to use a 1:12 twist on their rifles if the shooting world has moved so far beyond them.

That article is a pile of steaming schit...

My AT shoots 175 grain through the same hole if I do my part.

Tried it with the BH 178 A-Max and the new Federal 185 grain Juggernaut...guess what shoots like a dream even though ballistically it would be unstable from a 1:12 twist. Not saying that a 1:10 may be better spin stabilized as the velocity drops but to say retire the 1:12 because it can only do well with 168 grain crappy bullets is hilarious

 

[WirgmanUSMC]

Seems like the trend seems to be faster and faster twists. I don't wanna get left in the dust, so the last barrel I had put on my .308 was a Hawk Hill 1-9. The lightest bullet I shoot is a 175, and they have been shooting great out of it. I haven't had a chance to reach out with it, but I'm going to The Guardian shoot first weekend of April and we will see how it does. I plan on doing some nice subsonic loads for it for fun with my can, and I'm sure the twist rate will make that an easy process.

 

[phlegm]

your AX308 comes with a 1:10 twist so it should do better with the heavies. The AT comes with a 1:12 twist. Why? I have no idea. Its pretty dumb. The barrels are interchangeable but I not sure any retailer is going to be willing to swap barrels off 2 new guns in their inventory to satisfy a customer. If there is, please let me know and I will buy it from them all other things being equal!

Not exactly. Mine has a 1:11.25 twist.

 

[damoncali]

There is nothing wrong with a 12 twist, and AI uses them for a reason. That article is specifically discussing long range applications (1,000+ yards or so), and he's really splitting hairs with the twist rate. Yeah, when you look at F Class rifles (for example), your'e going to see some faster twists, heavier bullets, and the like. But you'll also see 30" barrels and longer than mag length rounds - because a .308 is mandated by the rules and practicality doesn't matter. The 12" twist makes a lot of sense when you consider a primary use of under 1,000 yards with magazine fed rounds. You're not going to be shooting 200 grainers in that case, and if you're really concerned about a dedicated long range rifle, you've chosen the wrong cartridge to begin with.

And for a little more context, there are a hundred things that matter more than an inch of twist. Buy with confidence and forget about it. Just don't try to feed it any 215 grain bullets.

 

[81sfo]

My AI factory Lothar barrels are both cut at 18" and are 12 twists... i can say that i get faster velocities than the 10 twist Aina Bartleins and i have shot up to 190s and 200 Berger hybrids with 2000mr powder no problem. Dont waste $400 to get a 10 twist.

 

[FF05]

your AX308 comes with a 1:10 twist so it should do better with the heavies. The AT comes with a 1:12 twist. Why? I have no idea. Its pretty dumb. The barrels are interchangeable but I not sure any retailer is going to be willing to swap barrels off 2 new guns in their inventory to satisfy a customer. If there is, please let me know and I will buy it from them all other things being equal!

My AX308 arrived last month, and according to the owner's manual it has a 1:12 twist.

 

[03psd]

My AX308 arrived last month, and according to the owner's manual it has a 1:12 twist.

interesting. One thing I have learned is that anything is possible with AI. Unless im crazy i swear their catalog states the AX comes with a 10 twist. Who did you order yours from? Is it a current production rifle or old stock? Either way it will be a shooter. Find what it likes, feed it that and be happy.

 

[Upstate43]

I'm of the opinion that there is no use for the .308 when you could have a creedmoor.

You're kidding right? I get that there are newer cartridges, like 6.5 Creedmoor, that have better ballistics out at range. But there is a big difference between hitting a target at distance and putting one down at distance. Go check out Big Game Rifles and Cartridges and Bryan Litz's Applied Ballistics for Long Range Shooting. They both talk extensively about the lethality of rifle bullets and Edward Matunas' Optimal Game Weight formula for determining the appropriate bullet weight and caliber for various game weights at various distances. Both books provide some very good estimates (this isn't an exact science) as to how the various cartridges perform at various ranges. 6.5 does very well on medium-sized game (think smaller-sized deer) out to 650 yards or so. Anything bigger than that or further out, the 6.5's lower mass (which factors into its terminal energy and momentum) starts to impede its capability.

I'm not saying that 6.5 is only good for deer. I'm sure if you get close enough and use good shot placement, it takes down bigger targets. But I encourage you to go check out that Optimal Game Weight formula; .308, and other .30 caliber based cartridges, have some definite lethality advantages out at range, despite their BC deficiencies relative to the 6.5.

OP, I've shot a 1:12 FN SPR extensively with both 168gr and 175gr match grade ammo. The 1:12 twist isn't a real problem the way some people make it out to be, so long as you have an appropriate length barrel. With my 24" barrel, I've had very good success sending those two bullet types out to 800 yards and a bit beyond. I haven't tried the bigger bullets (like the 180gr) yet, so I have no input how they would perform in a 1:12 twist rate. If you're looking for a shorter barrel (anything below 22") then I could see where a 1:10 twist would make sense. For the traditional barrel lengths I've seen on long range .308 setups, 1:12 or 1:11.25 have proven to be more than adequate for most of the match grade options out there. If you are sticking with .308, keep the barrel length in mind. There have been some reviews of .308 barrel length vs muzzle velocity (see attached); 24" seems to be a good compromise between having an ungainly 28" barrel and having too short of a barrel. 20" (with the appropriate twist rate) is probably as short as you'd want to go for long range applications.

 

[Upstate43]

Holy shit,this is fucking HILARIOUS! If you gotta read a book on killing,you are done before you start. Hint.

Brace yourself,but impact velocity plays more than a "small" role in Terminal Effects. Hint.

"Mass" means less than dick.

I see this kind of argumentative loud mouthing all the time. So I guess by your logic, a sewing needle or, to be more realistic, a 77gr .223 round traveling at 2,500ft/sec is just as capable of killing a bull elk as a 165gr .308 or .30-06 round traveling at the same speed?

Mass is a major factor in a bullet's kinetic energy, even more so in it's momentum (which plays a huge role in target penetration). If you really think that mass, and by extension kinetic energy and momentum, mean "less than dick" when discussing a bullet's lethality, then I guess you and I live in entirely different worlds have nothing else to talk about.

Do yourself a favor and go check out those two books I mentioned...they provide some very good information on this topic.

 

[Upstate43]

You are "educated" wayyyyyyy beyond your "intelligence".

Now in fairness,I could write more than a few books. Hint.

"Mass" and "energy" are Window Licker feel good notions. ALL fucking bullets of like diameter/weight,share IDENTICAL mass and S/D values,despite running the gamut in their integrity. Their Terminal Effects will be greatly skewed,despite the commonality of hypothesized bullshit,that has no bearing. Hint.

Further,those like bullets will also run the gamut in their aero-form,which more than a "little",skews how they literally impact upon victims. Hint.

I'd be impressed,if you could cite anyone that had more SMK disdain than I,for terminal Effects. Hint.

Pass the 75gr Hornie HPBT's and hold the Fluff. Hint.



You cannot begin to fathom your INCREDIBLE Stupidity.

Hint.

I get the feeling that the know-it-all's on this site are going to be a lot more belligerent than they were on the scout site.
I really don't get what you're hinting at.
Nor do I understand what your pictures are supposed to demonstrate. I guess anyone and everyone who has shot a bear or deer knows everything there is to know about ballistic theory? If that's the case, then there should be several hundred thousand "experts" on this subject.

You're derisive tone and slang doesn't mask that your saying truisms: "ALL fucking bullets of like diameter/weight,share IDENTICAL mass and S/D values,despite running the gamut in their integrity."
Yeah, no kidding. I was comparing bullets of different weights, not the same weights. Nor was I discounting the role that bullet construction plays in this subject. I'm simply stating that all things being equal, or nearly so, a heavier bullet will produce greater kinetic energy and momentum which is a factor (though not the only factor) in determining its lethality.

Now you may not agree with that, but there are well-respected individuals who have actually written books on this topic (which goes a step or two beyond the books you claim that you "could write") and I'm sure these people even have a few game animals under their belt. I'm not claiming to have the same understanding of this topic that they do, but I have read their work and it makes sense to me. If you want to post another foul-mouthed comment with pictures displaying your shooting prowess, go right ahead. You seem firm in your beliefs, and I'm not inclined to get in a pissing match with you.

 

[Upstate43]

Nothing I said was subjective and it's simplistic fact. Nothing more,nothing less. Hint.

You cited particular platforms and I'm rather at ease in connecting dots with water under the bridge,that flowed with same. Knowing me,I likely shoot a few different chamberings and have likely seen more than one bullet. Hint.

I get a kick out of some dumbfuck that reads bullshit out of a book and then thinks she has a fucking clue. Sugar...you most assuredly do not.

Hint.

A betting man would say that you, or at least your current profile, is not long for this forum.

Enjoy the rest of your day!

 

[FF05]

interesting. One thing I have learned is that anything is possible with AI. Unless im crazy i swear their catalog states the AX comes with a 10 twist. Who did you order yours from? Is it a current production rifle or old stock? Either way it will be a shooter. Find what it likes, feed it that and be happy.

The AX308 data sheet from both UK and US AI sites list barrel options as 1:12, along with the new colour options. Mine came from the UK, 20" with the new model fluted bolt and SFP (small firing pin). I also prior to purchase thought AX's had the 1:10 twist . I'm not too concerned, its a AI, it'll shoot...

 

[03psd]

The AX308 data sheet from both UK and US AI sites list barrel options as 1:12, along with the new colour options. Mine came from the UK, 20" with the new model fluted bolt and SFP (small firing pin). I also prior to purchase thought AX's had the 1:10 twist . I'm not too concerned, its a AI, it'll shoot...

No doubt about that. Interesting you mention the fluted bolt. My AT arrived with the fluted bolt as well. I wasnt expecting that. It has straight flutes. Is the fluting new and go along with the new small firing pins that they are supposedly using in all new (2015+) AT models?

 

[domdoc]

1:12 is a hangover from the days when 168-180 grain non-VLD bullets were all that was expected to go down the barrel of a .308 Winchester. That time has passed. Now, F-class and bullet development have made 1:10 the norm. Even faster if you expect to shoot the 215 Berger hybrid (and get max BC - I know, it may be accurate in 1:10), an equivalent Flatline, or Cutting Edge monolithic. Sometimes even if you plan to shoot a hunting bullet, like the Barnes TTSX. The .300 Magnum and even .30-'06 are always, to my knowledge, equipped with 1:10 twist barrels. No reason to put 1:12 on a general purpose .30 cal rifle. Note "general purpose," not specific applications, where slower twist is stipulated by bullet restrictions.

 

[FF05]

No doubt about that. Interesting you mention the fluted bolt. My AT arrived with the fluted bolt as well. I wasnt expecting that. It has straight flutes. Is the fluting new and go along with the new small firing pins that they are supposedly using in all new (2015+) AT models?

There's a thead further down the Bolt Action page 'Accuracy International - fully fluted bolt', not sure how to link.

I would have preferred the 1:10 twist with the 20" barrel, but here in Australia you don't get the option. Either you want a AI or you don't, take it or leave it... Saying that i did buy it with the intention of getting a 260Rem/6.5CM barrel.

 

[Upstate43]

1:12 is a hangover from the days when 168-180 grain non-VLD bullets were all that was expected to go down the barrel of a .308 Winchester. That time has passed. Now, F-class and bullet development have made 1:10 the norm. Even faster if you expect to shoot the 215 Berger hybrid (and get max BC - I know, it may be accurate in 1:10), an equivalent Flatline, or Cutting Edge monolithic. Sometimes even if you plan to shoot a hunting bullet, like the Barnes TTSX. The .300 Magnum and even .30-'06 are always, to my knowledge, equipped with 1:10 twist barrels. No reason to put 1:12 on a general purpose .30 cal rifle. Note "general purpose," not specific applications, where slower twist is stipulated by bullet restrictions.

Outside of hunting the big end of the big-game spectrum, who is using 215gr bullets for .308 platforms? F-class? Do any military or LE use it? Anyone in the PRS or similar organizations?

I know that Berger's 185gr bullet has gotten a lot of praise with the long range crowd. I suppose you could go with bullets heavier than that and get even better BC's than what the 185gr offers. Does barrel wear, magazine compatibility and barrel length become an issue with those bigger loads? I'd imagine at a certain point, it probably makes more sense to go with a .300 win mag or something comparable if you're trying to lob bullets that heavy for long range applications.

 

[domdoc]

Definitely F-class. I think it will be uncommon to see a .308 Win rifle shooting 1,000 yards in F-class with slower than 1:10 twist. 1:12 is likely not fast enough for the Berger 185 or JLK 180, for either hunting or F-class. SMK 190 is a fine, accurate bullet, and may shoot accurately in 1:12, but BC will not be optimized, and it is probably not going to win a 1,000 yard F-class match. Also, as I wrote, the Barnes TTSX and monolithic bullets in weights of 168 and higher may not stabilize in a 1:12 twist.

 

[Upstate43]

Definitely F-class. I think it will be uncommon to see a .308 Win rifle shooting 1,000 yards in F-class with slower than 1:10 twist. 1:12 is likely not fast enough for the Berger 185 or JLK 180, for either hunting or F-class. SMK 190 is a fine, accurate bullet, and may shoot accurately in 1:12, but BC will not be optimized, and it is probably not going to win a 1,000 yard F-class match. Also, as I wrote, the Barnes TTSX and monolithic bullets in weights of 168 and higher may not stabilize in a 1:12 twist.

I'll have to get my hands on some 185's and try them out for myself (my barrel is a 1:12). I've had no reason to complain about the twist rate so far, granted I'm not really into the F-class style of shooting.

 

[FF05]

I've shot plenty of F class, and have never been held back by a 1:12 twist. Most F class shooters here in Australia use 155gr 'palmer' projectiles out to 1000. A 175gr pill handles the wind better, but I've never needed to load anything heavier.

 

[domdoc]

Upstate: The Berger website lists 1:12 as the "optimal twist", but the newer numbers Berger is using in their twist rate calculator shows a stability number of 1.34 for the 185 hunting VLD at 2700 fps. That is just a hair under the old generally-accepted stability number of 1.4. Berger is now using a stability minimum of 1.5, which they show yielding the maximum ballistic coefficient. Even if the 185 VLD shoots well in a 1:12 barrel (and I hope it will), the ballistic coefficient is reduced by about 5%, according to Berger's best estimate. That won't really hurt your performance. However, with the Barnes TTSX, if a shooter runs the 168 grain TTSX boattail bullet through a 1:12 twist barrel, the load will most likely not group well. I have done this, and I thought somebody had lost their mind paying good money for Barnes Vor-TX ammo. Then I shot the same 168 grain Barnes Vor-TX in a 1:10 twist barrel. I got fabulous accuracy, and I totally changed my mind about the Barnes bullet, which I now highly recommend.
FF05: Comparison of wind drift using the Berger 175 VLD and the Berger 215 hybrid in 1,000 yard F/TR shooting shows that the 175 grain bullet will drift 20 more inches than the 215 grain bullet in a 10 mph crosswind. So if two competitors are using these bullets, and they both miss a wind call by the same amount, the shooter using the 215 will be closer to the center, and most likely get a higher score.

 

[MATADOR]

I think one thing that some are forgetting is that twist rate isn't everything in a barrel. Without accounting for other factors, i.e number of lands, height of lands, smoothness of the bore, how the throats is cut, the crown, etc etc also plays a big role in the outcome of that bullet once it leaves the barrel. Twist rate means nothing in stabilizing that bullet if the lands are shitty, if the crown is off, you get the idea. It's really hard to discuss twist rate as far as stabilizing certain length bullets without also accounting for all the other physical attributes of the barrel. A good quality 1:12 will outshoot a shitty 1:10 all day long.

 

[Lowlight]

Just call Mile High and have them switch it out for a US Bartlein Barrel those are 1-10... (WIN TAC)

These are TACTICAL rifles, not F Class, those guys are using really long barrels and super heavy bullets... they walk 5 yards from the trunk of the car to the line, any farther they use a cart.

The 185 is a great bullet, why do you think Federal Switched... they offer the Berger 185 as a factory load now. Yes you can shoot a 155 but unless you are shooting Palma why bother ... well if you are still stuck using a 1-12 maybe. But we certainly have better bullets today, and most of those are heavier.

Crappy lands and grooves LOL, who is doing that in 2017 -- Certainly not anyone making barrels for AI...

The WIN TAC barrels are Bartlein, WIN TAC makes barrels for AINA, get one and be done. You can spec an AI you don't have to buy it as it comes. Call Mile High