Please clarify Rate Of Twist as it pertains to choice of bullet

[persistentprogrammer]

I'm still confused on rate of twist and choosing the right bullet. Do you go with a smaller/lighter bullet for a slower twist, or other way around?

Thanks
.350 Rem Mag
T/C Encore 23 1/2 barrel 1-12" twist

[Questor]

Cartridges are designed in cooperation with rifle and handgun designers. The gun designers decide what rate of twist is most likely to perform well for the cartridge given the expected bullet weights and lengths. If you are using a longer than normal bullet, your gun may not stabilize the bullet because rate of twist is too slow. In that case your options are to use a different bullet or to replace the barrel.

This is only a significant issue with a few cartridges. 223 is the most notable because the guns were designed for 55 grain bullets and some people want to use bullets significantly heavier than that for either target shooting or big game hunting.

When researching a cartridge, read up on its history. Was it designed for a 40 grain bullet while you're intending to use 60 grainers? Could be a problem.

When ordering a custom gun make sure the maker knows what bullet weights you intend to shoot so he can select the right rate of twist.

[Catfish]

   Actually the weight of the bullet has no direct relation to the twist rate until you state what cal. the bullet is. It is the lenth of the bullet in relationship with it`s diameter that dictates the twist needed to stablize the bullet. A 1 in 72 twist was very command in muzzel loaders shooting round ball. The longer the bullet the faster the twist needed to stablize it. That is why it takes a faster twist to stablize a Barns copper bullet of a given weight than a lead jacketed bullet. What stablizes the bullet is the certain number of RPM`s., so you can get by with a slower twist rate with a round that shoots faster. That said, most of the time that really doesn`t mean anything since there is not enough difference is the bullets velosities to change the RPM`s enough to matter.

[GrampaMike]

The formula for the Idea Twist is:
MV is Muzzle Velocity
DB is Diameter of Bullet
LB is Length of Bullet

Minimum Twist Needed = ((MV / 56) + 115) * ((DB^2) / LB)

This seems to be a variation of the old Greenhill formula, but with muzzle velocity factored in.

Mike