Hello All,
What is the most popular twist used in 308 standard for the 155 gn projectiles?
Cheers
308 Twist
Moderator: Mod
-
Paul Janzso
- Posts: 573
- Joined: Tue Dec 13, 2005 1:10 pm
- Location: Mackay QLD
- Has thanked: 22 times
- Been thanked: 2 times
-
Chris Burdett
- Posts: 113
- Joined: Sun Jun 19, 2005 6:34 pm
- Location: NSW Australia
-
bolster55
- Posts: 410
- Joined: Tue Sep 16, 2008 10:46 pm
- Location: NE Vic
- Has thanked: 48 times
- Been thanked: 16 times
- Contact:
308 Twist
Thanks for the reply,
I have read several posts on twist ratio and they all say that to shoot 155's use a 1:14 twist but you both tell me that I can use a much faster twist. It seems that it is the same as 223, to shoot 80gn projectiles, use 1:8 twist but I use a 1:7 twist which works extremely well.
Thanks again for the reply, I will go a 1:10 or a 1:12 twist.
Cheers
I have read several posts on twist ratio and they all say that to shoot 155's use a 1:14 twist but you both tell me that I can use a much faster twist. It seems that it is the same as 223, to shoot 80gn projectiles, use 1:8 twist but I use a 1:7 twist which works extremely well.
Thanks again for the reply, I will go a 1:10 or a 1:12 twist.
Cheers
Why not use JBM's stability calculator and see what gives you the stability factor you need.
Look here: http://www.jbmballistics.com/~jbm/cgi-b ... ab-5.0.cgi
Bryan Litz's new book on ballistics includes software to do this as well. In Bryan's book he recommends a stability factor (Sg = gyroscopic stability) of Sg >= 1.4. An Sg less than 1 is unstable and longer projectiles require more stabilisation so generally the high ballistic coefficient bullets need more twist.
Use the JBM calculator and see for yourself, you need to know the length and weight of the bullet along with the muzzle velocity. The temp and barometric pressure you can leave the same and just enter different twist rates to see what stability factor you get.
Info on Bryan Litz's book: http://www.appliedballisticsllc.com/ind ... s/Book.htm
Look here: http://www.jbmballistics.com/~jbm/cgi-b ... ab-5.0.cgi
Bryan Litz's new book on ballistics includes software to do this as well. In Bryan's book he recommends a stability factor (Sg = gyroscopic stability) of Sg >= 1.4. An Sg less than 1 is unstable and longer projectiles require more stabilisation so generally the high ballistic coefficient bullets need more twist.
Use the JBM calculator and see for yourself, you need to know the length and weight of the bullet along with the muzzle velocity. The temp and barometric pressure you can leave the same and just enter different twist rates to see what stability factor you get.
Info on Bryan Litz's book: http://www.appliedballisticsllc.com/ind ... s/Book.htm
Menu
Newest members