Would the spin keep the bullet point first on the downward trajectory as long as there was even a slight deviation from the vertical?
Mr. niteowl77
For a slight deviation, probably not. In fact, the falling bullet would probably reorient itself to be perfectly vertical, base down.
Bullets in flight orient themselves in a way that all forces acting on them balance out. Drag is the biggest force, which explains why bullets typically follow a point first path -- it offsets the drag. You can overspin a bullet and it will keep it's attitude throughout its flight. Meaning it will keep the same angle relative to ground the whole way. Try launching a 40 grain .223 Remington from a 1 in 7 twist barrel. Many pistol bullets are overspun.