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308 Winchester rifling twist

 
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  #8  
Old 12-19-2010, 10:36 PM
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Re: 308 Winchester rifling twist

Quote:
Originally Posted by liltank View Post
For 168's and 175's? I would think a 1:12 would be plenty, but your the chief of the .308 tribe!

Tank
Thanks Tank: But I don't consider my self the chief of the 308s . I have had lots of experience with them
and there fore have an opinion based on shooting them at matches and at long distances
for many years. (600, 800, 900,1000, 1100 and 1200 yards) and have tried all of the .308 bullets
that were available at the time and the 168s were the best all round because of velocity and BC.

The larger bullets were used only under the worst conditions at 600 yards and drop was terrible.

The go to twist rate was 1 in 10 because of the velocity of the 308. With the big magnums
a slower twist is OK. The match grade rifles with a 1 in 10 would shoot anything but the ones
with the 1 in 12 would only shoot the 168s and 180s well. anything heaver would not stabilize
well enough to shoot long range.

But don't take my word for it look at what a premium barrel maker like Lilja recommends.
Even the big 300 RUM likes the 1 in 10 with any bullet weight.

And you are right, the 1 in 12 will work in the 308 if you stay with lighter bullets but if you try
the 180 and up you may not be able to get them to shoot well, and it does not cost more to get
a 1 in 10 barrel that will handle the 160s to 175s well.

Some of the bench rest crowd use less twist but the conditions and distance are better and they
can make them work within there needs.

I am not an advocate of tight twist just the best all round twist depending on velocity, bullet
weight and distance to be used with a particular cartridge.

Sorry BH; but the 168s were the bullet of choice for the 1000 yard matches in the 308s and if
they tumbled they would not have been.

J E CUSTOM
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  #9  
Old 12-19-2010, 10:58 PM
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Re: 308 Winchester rifling twist

I had very good results shooting LR matches with the 175 Bergers and SMKs at 1000yds out of my 1 in12 twist 26" barreled .308. I also tried the 180's but they just wouldn't work.

Gordon
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  #10  
Old 12-19-2010, 11:30 PM
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Re: 308 Winchester rifling twist

Sorry JE but 168s have never ever been used "successfully" at 1000 by anyone on a routine basis in a 308! That is just a cold hard fact that is undisputable.

You must be thinking of 600 which is the place that they have been used very successfully or possibly a few Garand (30-06) shooters that were able to use it sometimes succesfully..

In fact the 168 was designed for 300 meter matches in 1958 and is normally too short to keep stable at 1000 out of most 308 guns.

I have spent too much time in the pits at 1k watching keyholing bullets of anyone that tried to take the 168s at 1k in a 308.

All of the Sierra techs will tell you the same thing.

There is a very good reason why they ARE NOT shot today by anyone successfully at 1000. The dominant 308 round for 1k is one of the 155s, 175 or even the 185/190 Berger in Fclass today. You will never ever see the 168 on the line with a shooter that is not a newbie and then only once as they learn.

all you really have to do is go to the Long Range Target shooting forum where all the top 308 shooters hang out and do a little reading

Asa Yam is one of the best: here is his comments on the 168 SMK in a 308

Quote:
BAD IDEA.
There's an old saying in highpower shooting. "Friends don't let friends use 168s (Sierras) at 1000 yards." The 168 Sierra (and the post-1980 180s) are dynamically unstable in flight, and go unstable around Mach 1. We're talking about bullets flying through targets at large yaw angles, (90+ degrees to the line of flight), and highly erratic ballistics. Oh, you can make a 168 Sierra work at 1000 yards - if you can fire it at an MV of 2700+ FPS. There's a notorious load known as "G4" or "G8" that was a long time 1000 yard load using the 168 Sierra. The secret behind this load? 44+ grains of IMR-4895 in a Lake City casing.
BH

Last edited by BountyHunter; 12-19-2010 at 11:56 PM.
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  #11  
Old 12-20-2010, 01:46 AM
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Re: 308 Winchester rifling twist

For the 168 / 175 I would for sure go with a 12 twist.

That being said, Montanamarine over on snipershide has been using a 308 with a 12 twist with the 208gr amax to fairly good success. Several key factors are involved however. His ASL where he shoots / hunts is up around 4000ft or so, this is one of the bigger factors. He uses RL 17 to get the bullet moving right along. He uses Win brass and I think win LR primers, the brass has more case capacity than most others, so more powder. He also uses moly on his bullets. I think he also seats them beyond mag length, and single feeds them, though I could be wrong on this count. I would be the new Alliant MR2000 powder would do quite well. Short story is, they are probably right on the edge of stability.

For your stated needs, go 12 twist and don't look back. I think Howa has a 12 twist, certainly worth looking into if you do not already have a stick.

Have a good one,
Gary
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  #12  
Old 12-20-2010, 07:22 AM
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Re: 308 Winchester rifling twist

I use the 155's with a 1in10 twist. I can shoot out to 1300 yds with pretty good accuracy. The pics below were shot from my back yard at a Clorox bottle filled with water. The distance was 1235yds. If you look close you'll notice the the bullet mushroomed upon entry then did a "flip" inside the jug and tried to exit backward. It didn't make it through! That tells me the energy is gone and the bullet was pretty unstable at that distance but then again 1235yds aint too bad for a 308
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  #13  
Old 12-20-2010, 08:21 AM
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Re: 308 Winchester rifling twist

As mentioned, for 1K near sea level, the 168's will miss a six foot wide by six foot high target because they become so erratic at that distance. Every spring a couple of new guys will show at up f-class with Black Hills 168s and spray down the countryside.

I think my barrel twist is 11.25. It shoots the Berger, scenar and SMK 155 well enough with Varget and shoots the SMK 175s well also. The 175 SMK is a good hunting bullet for medium game.
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  #14  
Old 12-20-2010, 08:49 AM
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Re: 308 Winchester rifling twist

Quote:
Originally Posted by BountyHunter View Post
Sorry JE but 168s have never ever been used "successfully" at 1000 by anyone on a routine basis in a 308! That is just a cold hard fact that is undisputable.

You must be thinking of 600 which is the place that they have been used very successfully or possibly a few Garand (30-06) shooters that were able to use it sometimes succesfully..

In fact the 168 was designed for 300 meter matches in 1958 and is normally too short to keep stable at 1000 out of most 308 guns.

I have spent too much time in the pits at 1k watching keyholing bullets of anyone that tried to take the 168s at 1k in a 308.

All of the Sierra techs will tell you the same thing.

There is a very good reason why they ARE NOT shot today by anyone successfully at 1000. The dominant 308 round for 1k is one of the 155s, 175 or even the 185/190 Berger in Fclass today. You will never ever see the 168 on the line with a shooter that is not a newbie and then only once as they learn.

all you really have to do is go to the Long Range Target shooting forum where all the top 308 shooters hang out and do a little reading

Asa Yam is one of the best: here is his comments on the 168 SMK in a 308



BH

OK .

I'm not going to argue with you about it because you can use anything you want to. "BUT" I
competed for 12 years in the match game. and Loaded only two bullets for my 308 and they were
the 165 GKHP and the 168 SMK and I even managed to win the 1000 yard matches several times
and lots of 6,8and 900yard matches.

I had a 40x Range master with a 27+inch barrel and It was very competitive as long as I loaded it
hard. It had a 1 in 12 twist and would not shoot the heavy bullets at all.

Other competitors recommended the 1 in 10 and when I built my custom that is what I built it in.

I don't Like to boast but for the sake of this post I will mention that I have many match and class
wins with this combination and even a few state wins in the NRA palma and National matches.
So Maybe I am just lucky.

I know there are new Bullets that could be better but I know what worked and have not changed
my mind.

You also said that some use a 155 gr ? why would a 155 work and not a 168?

I still have my match rifle and it will still shoot sub 1/2 moa with Iron sights.

As you know all rifles are different but as this post was about twist rates all of my 30 cal rifles are
1 in 10 and will perform with the best of them.

So that is still my recommendation especially for the 308.

Nuff Said: you may have the last word.

Sorry we don't agree, but isn't that what makes the world go round.

J E CUSTOM
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