F T/R Competition Is 12 Twist Fast Enough?

[HighRez]

I'm just starting to hand load .308 with the intention of shooting F-T/R. In doing all my research on various bullets, BC's and barrels, I've noticed that the Savage F-T/R has a 1:12 twist barrel. Yet studying the various offerings in Bryan Litz' book, the Bergers in particular above 168 gr. are only marginally stable or below acceptable levels with a 12 twist according to Litz. The heavier SMK's are another story all together, acceptably stable in 13 twist barrels, again according to Litz.

Knowing the popularity of Berger bullets with F-Class shooters and the reputation the Savage F-T/R has as a competitive out of the box rifle, what's the real-world story? And to those of you shooting custom guns or re-barreling, what twist are you using? With the amazing BC's of the heavy Berger Hybrids and VLD's, if Bryan is correct (blasphemy), I'm thinking 1:10 is far more suitable than the 1:12 barrel Savage has chosen. Set me straight.

 

[Niles Coyote]

Re: Is 12 Twist Fast Enough?

Having several 308's of 12 and 11.27 twist the heaviest and/or longest bullet I have used is the 190 Berger VLD and also the 180 JLK LR VLD and they have been stable in all conditions for me at about 900ASL in all of my 308 rifles.

A few posters here are shooting 208 A-max from 12 twist Remington’s. However they may have altitude to their advantage... I don’t know as I have not tried them in mine.

I know of one f-class shooter at my range that uses a 1-13t for his F-class rifle...

It is my opinion that a 12twist is all you will need in a 308 unless you intend on shooting in extreme cold ( at or below 0) or at slower than normal velocity. But that’s only my opinion...

 

[USFTR]

Re: Is 12 Twist Fast Enough?

It depends on the specific bullet you want to shoot. For 185BT, I run a 12 twist. For the 200 hybrid, I'd say 11 twist. For anything heavier, 10 twist. I'd also recommend Berger bullets. I've shot Bergers for many years.

 

[Coletta]

Re: Is 12 Twist Fast Enough?

12 twist will be fine.

 

[pyrofx]

Re: Is 12 Twist Fast Enough?

I'm shooting a 12 twist in my 300 rem mag . I have shot 155 all the way to 208 amax . The 208 are squirting out at 2975 no problem . Keeps 6" at 1k off the bypod no problem all day long . I'm at 1100' at 127 degrees.

Greg

 

[hooksz86]

Re: Is 12 Twist Fast Enough?

I have the Savage 12 F/TR. For me the 168 SMK shoot real good and the 168gr berger shoots even better once I get out to 800-1100 yrd. Tack driver at 300 yards, take a golf ball every time. Have had as good as 7.5 inch group at 1000 yards with 13 shots/ 13 out of 13. cci br, lapua brass, 46.0 varget, 168gr SMK/Berger.

Just remember the twist is set to how long the bearing serface of bullet is not realy the weight of it. Even though those two things go hand in hand sometimes depending on the ogive of bullet.

I have not realy been around f-class shoots though. only at the house shooting and at one long rang shoot in amarillo.

 

[leadbullet]

Re: Is 12 Twist Fast Enough?

a quality 1-12 barrel and 175 SMk going plenty fast is all you need for F TR, reading the wind is way more important.
goos luck.

 

[kyle528]

Re: Is 12 Twist Fast Enough?

You should probably go with a 1:10 if you want to shoot long range, as some of the heavy bullets needed for long range will start to destabilize and fly all over the place.

 

[kyle528]

Re: Is 12 Twist Fast Enough?

you shoot 168's at distance? have you ever tried 175's or 190's at distance, they worked way better for me.

 

[gstaylorg]

Re: Is 12 Twist Fast Enough?

Remember also that the acceptable twist rates shown for projectiles in Bryan's book are based on projectile gyroscopic stability determined using optimal, marginal, and sub-optimal conditions for stability. On top of that, he is using a stability factor of 1.4 as the guide to whether or not a particular twist rate is sufficient for a given projectile under any of the three sets of conditions listed above. Using a stability factor of 1.4 as the guideline seems reasonably conservative, and doesn't necessarily suggest that a projectile with an Sg of 1.3, for example, in a specific twist barrel will suddenly become completely unstable and "fly all over the place" as suggested above. Many people get away with using a slightly less than optimal twist rate, particularly if atmospheric conditions are favorable.

You can't simply say that a 10-twist is necessary unless you know whether the specific projectile and conditions warrant it. Plenty of shooters use 155 gr loads with great success out to 1000 yd, or even farther. Even at such long ranges, 155s definitely do not require a 10-twist barrel to be stable. Ideally, you want to pick a twist rate that will sufficiently stabilize the projectile(s) you wish to shoot under the range(s) of conditions you can reasonably expect to encounter. In general, it's probably better to have a twist that's slightly faster than necessary than one that's much too slow, although an excessively fast twist rates can have undesirable effects in terms of greater spin drift and elevation changes caused by lateral wind (ie. the faster the spin, the greater these effects are). So the best idea is to [conservatively] use the minimum twist necessary, and the data in Bryan's book provide the one of the best possible resources to help you make that decision based on the projectile(s) you want to shoot.

 

[Helmet]

Re: Is 12 Twist Fast Enough?

My Savage 308 was a 1-10" twist and it really bothered me. No bullet that a 308 can properly push needs a twist that fast. Even the 190 Bergers didn't need that. I went ahead and shot 208 Amaxes, but I felt they were a bit heavy for the caliber. I think the fastest twist you would need would be a 1-11". A 1-12" twist would probably be fine. Berger doesn't say you need faster than a 1-11" until you move up to a 215 gr Hybrid and that's just too heavy for a 308. http://www.bergerbullets.com/Quick%20Reference%20Sheets%2010-28-11.pdf

Bullets only gain stability downrange so if it has enough stability leaving the barrel it will have even more stability downrange.

 

[SIE107]

Re: Is 12 Twist Fast Enough?

Most of the long range prone shooters that I know use a 12 twist barrel or a 11.25 twist now a days! The AMU uses a 11.25 twist in the M-110 and Berger 185 bullets. The newer style of 155's work a lil better in a 12 twist barrel. I know that Bryan has shot the Berger 185BT's in a 13 twist barrel with great success having shot with him and scoring him while doing it! So there are more factors than just picking a twist. But most of the long range competitors have pretty much figured it out for you already.

I will say this, your better off using the new versions of 155's or the 185's than the old school thought of 168's or 175's. Most F/TR shooters whom seem to be winning are using the Berger 185's. If it were me, I would be running a 12 twist barrel and would be using either Berger 155.5 Fullbore bullet or the Sierra 155 (2156) Palma bullet.

Also the lenght of your barrel may dictate what twist you may want to run, all my barrels are 30"s.

I noticed one poster stated that the lenght of the bearing surface is what dictates the twist of the rifling, that is close, rather it is the over all lenght of the bullet that should be considered, but then, that is not always the case either.

So pick a twist between 11.25 - 12 and you should be fine.

 

[scaxeman]

Re: Is 12 Twist Fast Enough?

HighRez,

I have shot the Savage 1:12 twist barrel for years. It has no problem stabilizing 185's or heavier pills.

The only application I have gone to 1:10 twist barrels for is 215's and 230's out of a .308.

If I was to buy a Krieger or other custom barrel, it would almost certainly be 1:11 or 1:11.25. This twist rate will stabilize any (reasonable) .308 F-T/R bullet, from a 155.5 up to a 200 grain (or 208, likely).

Hope this helps,

Darrell

 

[HarryBallz2029]

Re: Is 12 Twist Fast Enough?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: kwells308</div><div class="ubbcode-body">You should probably go with a 1:10 if you want to shoot long range, as some of the heavy bullets needed for long range will start to destabilize and fly all over the place. </div></div>
Im sorry but this comment does not make much since to me. Why do you say 1-12 isnt as good as 1-10 for long range? Twist has nothing to do with whether you can or cant shoot long range it comes down to how heavy of a bullet you can stabalize at range. There are alot of F T R class shooters that run nothing but 1-12 twists and do better then the 1-10 twist guys do.

 

[SIE107]

Re: Is 12 Twist Fast Enough?

I will have to agree with Darrel and DH on what they said!