Rate of Twist ?

[jerry d]

How does it effect accuracy? I've been looking at 308 caliber,rate of twist varies from 10-12 with the 3 different manufacturers i looked at. All had the same length barrel,22".

I also looked at the 7mm08 from the same manufacturers the rate of twist was 9.5

How do you know which rate of twist will make a certain caliber more accurate?

[jeepkid]

It won't make a certain caliber "more" accurate, it will allow you to stabilize bigger (longer) bullets so you can shoot those accurately without having them keyhole...

[jerry d]

Originally Posted by jeepkid

It won't make a certain caliber "more" accurate, it will allow you to stabilize bigger (longer) bullets so you can shoot those accurately without having them keyhole...

Ok.......but I'm not 100% clear on this so let me give you an example: winchester model 70 has a 1:12 rate of twist, remington has a 1:10 rate of twist which one should be more accurate with the heavier bullet ?

[jeepkid]

Originally Posted by jerry d

Ok.......but I'm not 100% clear on this so let me give you an example: winchester model 70 has a 1:12 rate of twist, remington has a 1:10 rate of twist which one should be more accurate with the heavier bullet ?

The 1/10 will stabilize a bigger bullet better, so it should also be more accurate with them. Unless a 1/12 will also stabilize the bullet, then either one might be the accurate one...

Heavier doesn't necessarily mean it will need a faster twist, the length of the bullet does, like VLD's will need a faster twist to stabilize compared to a round nose bullet.

[jerry d]

ok thanks Jeep.I got it now!!!

[Ridge Runner]

I always go a bit faster on the twist than needed it cuts your mv just a tad but doesn't hurt accuracy and the added spin on the bullet helps terminal performance (expansion)
lets crunch some numbers
308 diameter 190 gr at 2700 fps
in a 10 twist
2700x(12/10)x60= 2700x1.2x60=194,400 rpms
in a 12 twist
2700x(12/12)x60=2700x1x60=162,000 rpms
so you see a lil bit faster twist is alot as far as bullet rotation, weight doesn't matter its length, but heavier bullets are normaly longer, as you can see velocity also plays a big factor in how fast the bullet spins. you can stabilize a heavier bullet with the same twist in say a 7 rum than a 280 solely because of velocity.
RR

[jerry d]

Thanks Ridge that clears it up