Originally Posted by
Big Z
So, I'm trying to understand the behavior of gyroscopes and how they apply to bullets to explain drift. The obsolete "log rolling on water" theory just isn't cutting my curiosity. Now, tell me if I have this right in a simplified manner:
Rotating objects experience a push 90 degrees (in the direction of rotation) from where the force is applied. So, since bullets are dropping, the greatest force they are encountering is underneath them (dropping=hitting the air, or rather a downward acceleration implies the same). A right-twist bullet will then experience a drift as if it were being pushed from the left (which is 90 degrees from bottom of the bullet in the direction of rotation).
Do I have this understood properly in a manner, simple as it may be?
No you do not. I have a book called understanding firearms Ballistics by Robert Rinker. The reason for this effect does not have to do with the medium it is in. He specifically mentioned the log rolling on a water as a myth.
It has to do with the gyroscopic action when the axis of rotation is not parallel with the direction of the center of gravity which then causes a yaw in the flight, which steers the bullet to the side depending on direction of twist. I don't pretend to understand it, the above paraphrases wikipedia.
It is a phenomena of physics with a rotating body tipping as it flies through space. The change in direction is because the as the bullet's nose dives in trajectory, gyroscopic stability turns it to the side, and this yaw steers the bullet.
It is a small effect until the ranges get rather long.
And CZ, the RPM's of the bullet would still be roughly 180,000 rpm. The air resistance to rotation of the bullet is small, so the spin never slows down to much.
I recommend the above book if people are interested in ballistics. It isn't well edited, as there are spelling errors and the pictures aren't good, but it is considered an authoritative book on the technical apects.
It even covers the coriolis effect.