Determining optimal rifle twist using the Greenhill formula. - The Firearms Forum

sharpie443 · 10-02-2012, 10:40 AM

I got a question from someone on youtube asking why rifling and bullets in general haven't changed much over the years. His message boiled down to him wanting to know why we don't try to make better rifling to improve accuracy. Obviously there are a number of things wrong with his question but I don't think a lot of new shooters understand rifling or how we determine what twist will gyroscopically stabilize a round.

So I made a video explaining the Greenhill formula and how we determine what twist to use with different projectiles. I also talked about needing a faster twist with subsonic and things like that.

I figured someone here might be interested in it. The video involves math so I’m not sure how popular it will be.

http://www.youtube.com/watch?v=4WKzt...1&feature=plcp

stumpjumper · 10-02-2012, 09:04 PM

interesting. i take it this applies to handguns also?

68c15 · 10-02-2012, 09:41 PM

there. I finally learned something today. now I'm going to bed

sharpie443 · 10-03-2012, 12:38 AM

Quote:

Originally Posted by stumpjumper

interesting. i take it this applies to handguns also?

Sure. It works with any projectile. It was originally intended for use in rifled artillery. We have more precise methods for determining twist but this equation works fine for most applications. It's also the easiest to explain.

B27 · 10-03-2012, 01:27 AM

Most informative!
Thanks!

10-02-2012, 10:40 AM	#1
sharpie443 V.I.P. Member Join Date: May 2012 Posts: 56	Determining optimal rifle twist using the Greenhill formula. I got a question from someone on youtube asking why rifling and bullets in general haven't changed much over the years. His message boiled down to him wanting to know why we don't try to make better rifling to improve accuracy. Obviously there are a number of things wrong with his question but I don't think a lot of new shooters understand rifling or how we determine what twist will gyroscopically stabilize a round. So I made a video explaining the Greenhill formula and how we determine what twist to use with different projectiles. I also talked about needing a faster twist with subsonic and things like that. I figured someone here might be interested in it. The video involves math so I’m not sure how popular it will be. http://www.youtube.com/watch?v=4WKzt...1&feature=plcp -->

10-02-2012, 09:04 PM	#2
stumpjumper Senior Member Join Date: Jun 2012 Location: swflorida Contributor Posts: 655	Re: Determining optimal rifle twist using the Greenhill formula. interesting. i take it this applies to handguns also? __________________ after three rounds you're just making noise Guns have only two enemies rust and politicians

10-02-2012, 09:41 PM	#3
68c15 Advanced Senior Member Join Date: Nov 2011 Posts: 2,066	Re: Determining optimal rifle twist using the Greenhill formula. there. I finally learned something today. now I'm going to bed __________________ I'll go defenseless when our leaders do the same

10-03-2012, 01:27 AM	#5
B27 V.I.P. Member Join Date: Sep 2012 Location: Atlanta, GA Posts: 415	Re: Determining optimal rifle twist using the Greenhill formula. Most informative! Thanks! __________________ "Do not stand beside the road and argue with a fool...lest others in passing take you also for a fool."