I was looking at Sako 243 rifles and was surprised to see 1/10 twist listed. I had a Shilen custom barrel in 6mm made years ago in 1/10 twist and found it would not stabilize scirrocco 90 gr because they were too long. Why wouldnt they chamber these rifles in 1/9 twist? Was my experience unique?
243 6mm observation and question.
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Sunray
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My .243 is 1 in 9.125. 90's work just fine.
Sako is likely trying to cover light and heavy bullets.
Sako is likely trying to cover light and heavy bullets.
JRH6856
Member
The Sako follows Winchester's original twist rate for the .243.
The .243 Win /.244 Rem /6mm Rem story is an interesting one
Both Winchester and Remington introduced a 6mm round in 1955. The .243 Winchester was originally chambered in a Model 70 with a 1:10 twist which allowed it to adequately stabilize 100-110 gr bullets. The .244 Remington was initially chambered in a 722 with 1:12 twist which would not stabilize longer bullets generally limiting it to 90gr or less. The heavier bullets in .243 prooved more popular with deer hunters and Remington tried to recover IN 1958 by chambering the .244 in a 700 with 1:10 twist. Eventually, (1962) they renamed the .244 to 6mm Rem and chambered it in the 722 with 1:9 twist. This compromised the superior accuracy of the .244 722 with lighter bullets but allowed adequate stabalization of any commercially loaded 6mm bullet weight.
The 90 gr Swift Sirrocco is long for its weight, and Greenhill's shows a 1: 7.8 twist to be optimal, but I would think that it would still stabilize at 1:10.
I'm in the process of working up loads for my cousin's .244 Rem and the 1:12 twist is limiting me to shorter, lighter bullets. 90 gr will stabilize, but 95 and heavier get a bit wild.
The .243 Win /.244 Rem /6mm Rem story is an interesting one
Both Winchester and Remington introduced a 6mm round in 1955. The .243 Winchester was originally chambered in a Model 70 with a 1:10 twist which allowed it to adequately stabilize 100-110 gr bullets. The .244 Remington was initially chambered in a 722 with 1:12 twist which would not stabilize longer bullets generally limiting it to 90gr or less. The heavier bullets in .243 prooved more popular with deer hunters and Remington tried to recover IN 1958 by chambering the .244 in a 700 with 1:10 twist. Eventually, (1962) they renamed the .244 to 6mm Rem and chambered it in the 722 with 1:9 twist. This compromised the superior accuracy of the .244 722 with lighter bullets but allowed adequate stabalization of any commercially loaded 6mm bullet weight.
The 90 gr Swift Sirrocco is long for its weight, and Greenhill's shows a 1: 7.8 twist to be optimal, but I would think that it would still stabilize at 1:10.
I'm in the process of working up loads for my cousin's .244 Rem and the 1:12 twist is limiting me to shorter, lighter bullets. 90 gr will stabilize, but 95 and heavier get a bit wild.
My experience was that the 90 scirroco would not stabilize in 1/10. Maybe other's experience is different. For me I dont understand why all quality 243/6mm hunting rifles would not be 1/9. When I saw 1/10 in the Sako it gave me pause.
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JRH6856
Member
I haven't even considered loading the 90gr Sirrocco because of the length. The bullet is longer than many 100gr and some 105gr bullets. The lighter weight might be an additional factor. I'm sure it won't stabilize in a 1:12 barrel.
In theory, 1:9 should better stabilize longer bullets, but I wouldn't think the difference between 1:9 and 1:10 would be a go/no go.
Sorry I can't be of more help.
In theory, 1:9 should better stabilize longer bullets, but I wouldn't think the difference between 1:9 and 1:10 would be a go/no go.
Sorry I can't be of more help.
JRH6856
Member
If that "older 6mm" is marked .244 Remington, it has a 1:12 twist. If if is marked 6mm, it has 1:9. Unless it is a 700 in .244 IWC it is 1:10.
243winxb
Member
Remlngtons 40x in 243win. is available in 10, 12,14 twists. My 10 twist likes Bergers 90gr hpbt but nothing longer.
Corn-Picker
Member
I'm ignorant on the topic of spin stabilization so excuse the naive question, but what's the disadvantage of fast rifling? There must some be some downside to overspinning a light bullet or everyone would use a 1 in 7 twist for everything.
Light bullets in a fast twist barrel can be spun so fast that they disintegrate upon leaving the barrel. Twist rate and velocity the rifle can obtain controls the spin of the bullet (revolutions per minute).
This is why high speed cartridges such as 220 Swift and 22-250 tend to have slower twist barrels than say a 223 Remington
This is why high speed cartridges such as 220 Swift and 22-250 tend to have slower twist barrels than say a 223 Remington
Fella's;
I couldn't care less about stabilizing 100 grain bullets, or the Sirocco in that size bore. I found the Speer 90 grain spritzer and am not looking back. Speer builds this bullet heavier for the old 1:12 twist guns, but it doesn't matter, they shoot pretty darn fine in my faster twist gun. The performance on deer is great. I've shot both mulie and whitetail with it & DRT. Perfectly adequate performance when put in the boiler room, and as a plus, hit a mulie in the shoulders & drilled the first, opened up nicely and was found just under the skin after breaking the off shoulder.
It's a sad fact that this bullet is hard to find these days, but I think they can be had through Midway. I'll take the increase in velocity over the 10 to 15 grain heavier bullets, and enjoy the terminal performance all the way to the table.
900F
I couldn't care less about stabilizing 100 grain bullets, or the Sirocco in that size bore. I found the Speer 90 grain spritzer and am not looking back. Speer builds this bullet heavier for the old 1:12 twist guns, but it doesn't matter, they shoot pretty darn fine in my faster twist gun. The performance on deer is great. I've shot both mulie and whitetail with it & DRT. Perfectly adequate performance when put in the boiler room, and as a plus, hit a mulie in the shoulders & drilled the first, opened up nicely and was found just under the skin after breaking the off shoulder.
It's a sad fact that this bullet is hard to find these days, but I think they can be had through Midway. I'll take the increase in velocity over the 10 to 15 grain heavier bullets, and enjoy the terminal performance all the way to the table.
900F
RainDodger
Member
I have a Sako Forester (L579) heavy barrel .243. It has a 1:10 twist and I had a heckuva time working up any decent load for it until I found Berger's 90 grain boat tail HPs. They must be shorter than a Scirocco, I guess, because they stabilize just fine.
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