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# Twist Rates and Velocity?

#36
03-13-2013, 02:42 PM
 Silver Member Join Date: May 2009 Location: Prosperity, Pa Posts: 352
Re: Twist Rates and Velocity?

Montana said that with the same muzzle velocity, regardless of barrel length ,the spin would be the same. I totally agree with that. With a 1 in 9 twist, the bullet rotates once each 9 inches of travel . If a 1/9 travels 81 inches in one minute , it would have revolved 9 times thus would have 9rpm. Same bullet travels same distance in 30 seconds, now is rotating at 18 rpm. When it travels at 3000 feet/ second ,it rotates at 240,000 rpm. The faster it goes, the faster it spins, but still rotates only once for each 9 inches traveled. If you go to a 1 in14 twist, the 3000 fps bullet only rotates at 154,286 rpm. That is why some light varmet bullets don't do well in high speed fast twist situations. 300 thousand rpms tends to be hard on the pistons!
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Phil Conklin.... Shooting Instructor for The Best of the West
#37
03-13-2013, 05:25 PM
 Platinum Member Join Date: Dec 2005 Posts: 2,110
Re: Twist Rates and Velocity?

Here's another "twist" in this very interesting thread. . . .

Which rifling twist presents the greatest angle of the lands to the bullet?

30 caliber, 1:11 twist

22 caliber, 1:8 twist

And thanks, Edge, for finding then posting those "unbalanced bullet" pictures. Those tests are exactly what Dr. Frederic Mann did in the early 1900 testing unbalanced lead bullets in his "Mann rest" barrel. It was published in his book "The Bullet's Flight from Powder to Target" that came out in 1907. Pretty savvy shooting stuff from a well known surgeon at the time.
#38
03-13-2013, 07:11 PM
 Platinum Member Join Date: Nov 2005 Posts: 1,081
Re: Twist Rates and Velocity?

The Mann rest is pretty interesting, I had to look it up

I also found the article that those pictures came from for anyone interested in reading:

Bullet Imbalance by Harald Vaughn

Bullet Imbalance

edge.

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