Thread: Projectile vs barrel length

Heavier calibers, such .308 upwards will have rifle especifications different for the purpose they are build for, a varmint 308 is likely to have a slower twist rate to push lighter projectiles faster at shot and medium range(bush or small fields(up to 300mt max?)), other 308 version designated to further distances the shooter will desire a faster twist so they can shoot heavier projectiles with less athmosferic influence in its path.
A heavier caliber such the .375 mentioned by KiwiGreg is categorised by me as a special caliber and as you can imagine it is designed to hit things at a very long distance. These calibers are designed with barrel length and twist rate ad equated to the purpose of the projectiles being used to reach those distances. Many people wanting a rifle to an especific purpose (long-extreme range) normally build the rig to suit their needs, a .308 or 300WM with 1:10 or 1:9 twist, a Creedmoor with 1:7(not really need, just example) a .243 normally 1:10 with a 1:8 or 1:7", a 7mm normally 1:9.5" to a 1:8.5" and etc.
Do a quick google about magnums and ultra magnums caliber, apparently the ultra magnums have a bit faster twist than the normal magnums.

Again, I hope I am of some help.