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Double Rifles, Single Shots & Combinations >> Building Double Rifles & Gunsmithing

NitroX
.700 member

Reged: 25/12/02
Posts: 39877
Loc: Barossa Valley, South Australi...

Re: The Greenhill Formula for calculating barrel twist rate
21/08/22 05:37 PM

Let's try it.

A Woodleigh .333 300 gr SP. 1.459".

T= (150 x D)/R

Where:
T- is the twist required (number of inches per one revolution)
D- is the diameter of the bullet (in inches)
R- is the ratio of bullet length to bullet diameter (length divided by diameter)

(150x.333)/(1.459/.333)=11.4"

If it is resized to .330 = 49.5/4.4212 = 11.2"
assuming no additional length.

A .330 250 gr resized to .323" bore:

1.302" 250gr SP .330 = 48.45/4.0310 = 11.24"
1.419" 250gr FMJ .330 = 48.45/4.3932 = 11.03"
i.e. for resized to a .323 bore.

--------------------
John aka NitroX

...
Govt get out of our lives NOW!
"I love the smell of cordite in the morning."
"A Sharp spear needs no polish"

Post Extras

Entire topic
Subject	Posted by	Posted on
The Greenhill Formula for calculating barrel twist rate	NitroX	21/08/22 05:20 PM
Re: The Greenhill Formula for calculating barrel twist rate	NitroX	21/08/22 05:23 PM
Re: The Greenhill Formula for calculating barrel twist rate	LRF	22/08/22 06:39 AM
Re: The Greenhill Formula for calculating barrel twist rate	NitroX	21/08/22 05:37 PM

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