My 3 primary .30 caliber rifles have 1:12, 1:10, and 1:8 twists respectively. The only bullets I have been unable to fully stabilize in the 1:12 are 240 gr Woodleighs, and therefore by extension, the very long 230 gr VLDs. The 1:10 twist has been the .30 caliber standard since the 1890s when .303s and .30-40s drove long 215 and 220 gr round nose bullets, propelled by charges of the new nitrocellulose powders, at the blistering velocity of 2000 fps. Given lighter modern bullets, that are similar in length, but with much higher BCs, and velocities half again faster, it was seen that a 1:12 was suitable for 95% of the applications that a .30 caliber rifle is suitable for. Why then would some idiot spec out a .30 caliber barrel with a 1:8? Well, what happens if you want to reach out to a mile with your .308?
We know that bullets can become unstable as they slow through the transonic range, and finally become subsonic. This, despite the fact that the bullet's rotational velocity changes little during it's time of flight, although it's linear velocity has been reduced by two thirds. What's the old saying? Friends don't let friends shoot 168s at 1000. The answer to the problem is greater stability. Greater stability really means a more rigid stability, and that gain in rigidity is created by higher rotational velocities. Since its not practical to attempt to increase the linear velocity of a bullet from any given cartridge, the easiest way to increase it's rotational velocity, is to increase the rate of twist; so I chose the 1:8 for my .308 target rifle.
You will never run into a problem with your 1:12 shooting out to 800 yards with any mid weight match bullet, and 1000 yards shouldn't be a problem if you're shooting 155s or 175s.
