Sounds like you're heading for the 'fuzzy' areas.
There's a bunch of stuff happening to the bullet as it flies. There are 'external' forces, wind, twigs, rain, etc.. there are also 'internal' forces variable on spin, bullet concentricity, jacket thickness variations, center of mass and center of rotation, there is also earth's rotation. It's fairly amazing that we can hit anything with a rifle at any distance greater than an inch or two beyond the muzzle [img]images/icons/grin.gif[/img] .
I believe the one you're heading for is commonly called 'spin drift' or I believe also known as Magnus effect/force. It's the same principle as a throwing a curve ball in baseball.
Yaw as I understand it, is caused by forces acting on the bullets' gyroscopic stability, a low pressure area is trying to lift the front of the bullet as it flies forward while falling, this causes the bullet's nose to deviate 90 degrees from the lift force. I don't believe thhis would cause as much trajectory alteration as 'spin drift' as long as the bullet remains in a non-tumbling state.
There is a lot of information available on the web about these effects and there are some knowledgable folks here too!! It's an area I don't know a lot about and will stay away from any significant technical aspects.
At the distances I shoot and the degree of accuracy I accept and the nature of my targets it's not an immediate issue for me.
There is a book that may cover a good deal of this info, it's authored by a fella that visits this board on occasion, I can only think of his posting name TriggerFifty. I'll look it up and be right back.. Dean Michaelis
Here's a site that has some ingo on Dean, Warren and the long range rifles and shooting.