LouW and Rotaryphile are dead nuts on, regarding trajectory and sight picture. The thing about bullets being tail heavy...etc, May apply to a low velocity round (generally considered around 1500 fps or less), but in a rifle I would seriously doubt it. The spin imparted by the rifling would stabilize the projectile enough that the precise balance shouldn't matter, although rifling can have other undesireable effects; the bullet weight and number of turns of the rifling in the barrel can cause a "dutch roll" effect where the bullet travels in a sort of corkscrew path. This is usually with a lighter slug and a barrel with a lot of twist. It's amazing to me that just the little bit of twist (say 1 turn in 12 inches or even 1-in-14) can impart a spin on the bullet in the neighborhood of 100,000 rpm or better. I used to know the formula to calculate bullet spin, has to do with bullet weight, muzzle velocity and number of turns of the rifling, but I had to dump it from my mental harddrive in order to make room for airplane stuff. This spin is what can cause a bullet to ricochet so easily, and in some cases even explode due to the centrifugal forces tearing the bullet apart.