Barrel twist

[FNWhelen]

I read a lot where folks are going to faster twist barrels to be able to shoot longer bullets. So what is the downside and how do you know the limit? I understand caliber plays a part as does velocity but are there guidelines?

 

[Guy Miner]

Choose the barrel twist for your intended bullet.

Most of the bullet makers are good about specifying which twist their long range bullets require.

 

[xphunter]

What Guy said.
If you have a different range of bullets you want to use or try, get the twist rate for the longest/highest BC one you intend to use.
The one that requires the fastest twist.

 

[Idaho53]

I have seen bullets come apart from over rotation due to incorrect twist/bullet combo. I had a good conversation with Hornady, and the formula they use for match grade type bullets is to keep bullet revolutionary under 300,000 RPM's, using the following calculator: RPM calculator is Velocity x 720 and then divide by twist rate
Examples:
3,000 FPS x 720 / 7.5 = 288,000 RPM
3,000 FPS x 720 / 7 = 308,571 RPM

 

[FNWhelen]

I have 40 year old custom rifles that have too slow of twist for some modern bullets. But who knew back then we would have todays bullets. So if building a new gun should a guy try to get close to 300,000? If 300,000 is the high side what is a good number for too slow?