imported post
"Longer bullets will tend to do this over short, stubby bullets, in general."
Right, which is known as
precession; basically, the axis with the greatest potential momentum tends to be the one where rotation is most stable. In an absence of resistance from air, a cylinder tends to rotate around the middle point, rather than perpendicular to its long axis.
How a bullet will travel once it hits an object of varying density is difficult to predict, particularly if the object is dense enough to cause deformation of the bullet (which also varies as the material hardness of the bullet material, i.e. lead vs copper jacketed). It also has a great amount to do with the energy of the bullet at the time it strikes; is it mostly expended due to long range, what is the mass, speed, and cross section (important because it changes theforce necessary to penetrate)of the bullet?
Another factor is the rifling of the barrel. Higher twist ratio produces higher rotational velocity, which is good for improving the stability of the bullet, at least right up to the point wherespeed and rotation cause the bullet to disintegrate as it leaves the barrel because it creates more "centrifugal force" than the structure of the bullet can handle.
Length of the barrel changes the time-under-acceleration of the bullet. So generally, a longer barrel means more FPS before it goes ballistic and starts to slow down. Faster bullet speeds tend to have flatter trajectories. Slower bullet speeds tend to be more affected by air movement and density, for the same mass and cross section (more speed/mass equals greater total energy).
At extreme long range, pretty much any bullet will tumble a certain amount. Mostly, you would have to shoot fairly high in the air for a bullet to get to this state before it grounded.