.223 Build Question. What twist rate

[35Whelenshooter]

I have a .223 build that I'm in the process of doing.

1. What twist rate should I consider using for this build? I will be using it for varmint hunting as the primary role for it. Second I would like to be able to use it as a back-up deer rifle.

2. Bullets; I have over 12,000 Hornady 55Gr. Spire Points, #2266 along with several 1,000's of the 77Gr., 80Gr.

3. The 1/10 twist is the standard. 1/9 should handle the 75Gr. & 77Gr. but I think my need for the 1/8 would be my best bet. 1/8 should handle a good selection of bullets.

Thank you all in advance for all the reply's.

[StandingTall]

I agree...a 1/8 twist rate would be the best for those 75 and 77 grain bullets you have. It will also be fine for your 55 grain bullets.

[RP12]

1 in 8, you won't regret it.

[cvx444]

For an evaluation of bullets ballistics see JBM Ballistics. http://www.jbmballistics.com/ballistics/calculators/calculators.shtml
For the stability numbers (twist rates) - http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi

Primary factors affecting twist rates / bullet stability are -
Bullet Length
Atmospheric Temperature
Altitude

Unless you use a very long (heavy) VLD bullet, near sea level, in very cold conditions, a 1 in 8 twist is OK and typically easier to get.
The early M-16's had a 1 in 14 twist until they tested them in the arctic.

However for my new Savage I decided to wait the extra time for a 1 in 7 twist, since I may use it for 600 and 1000 yard shooting. For me the faster twist was cheap insurance, but your needs are probably different.

Mike L in TX