green hill fourmula

[johnson1942]

i tried to post a question to every one last night and i dont see it. i will try again. please post your good or bad experience in using the green hill fourmula in makeing the perfect twist for various round ball cal. i know their are many other factors but the twist rate is important. i have very good succes using it for long cast bullets but i havent been satisfied in useing the green hill formula for roundballs. i want to learn every thing i can about twist rates and roundball accracy. thanks johnson1942.

[Naphtali]

Here is a link to an index of calculators, among which is a stability calculator. This is, I believe, what you seek in terms of precision.

http://www.jbmballistics.com/ballistics/calculators/calculators.shtml

Hope this helps.

[451 Pete]

Johnson 1942
A very good reference guide on ballistics is available in the book titled " Understanding Firearm Ballistics " by Robet Rinker . In his book he states " Muzzle loaders can benefit from a rifled barrel , but there is no precise figure on what the twist should be." This statement is backed up also by an earlier book " The Complete Black Powder Handbook " by Sam Fadala where he basically says the same thing.

There is a range of twist rates for any size round projectile that will work. A round ball does not require a fast twist to stabilize. One example is a .32 cal. round ball. It will stabilize at a 1:30 or a 1:50 twist rate depending on the velocity imparted to the ball. Too high of a velocity at the faster twist rates can cause problems with the ball stripping the rifling. The slower twist rate will stabilize the round ball being driven at a higher velocity but if the ball is driven too slow with a very light load it can de-stabilize.
The larger the round ball projectile is in mass ( or size, diameter ) the less revolutions per second it needs to stabilize. So your best or optimum rifling twist for any given caliber with a round ball is a range being determined by the bore size and the velocity at which you are shooting the round ball. That is the main reason that most books on the subject will talk about working up the load for your rifle as each rate of twist and caliber will have a load that will optimize the accuracy of a particular rifle.

Hope this helps ... Pete

[HARRYMPOPE]

rinkers book is great and a must read.