[eternalfire1244]

"The spin axis parallel to the direction of flight helps maintain a straighter (more accurate) path because the projectile has ROTATIONAL INERTIA."

This is a valid argument, although in my personal experience the rotational inertia causes another type of inaccuracy- corkscrewing. This is especially true with barrels that are slightly bigger than the projectile, the ball bounces in the barrel and randomly bounces out of the muzzle. This action increases the "corkscrew effect".