The_Dunedan

There's also the fall position to consider; cylindro-ogival bullets like handgun rounds fall on their sides, while spitzers tend to fall tail-down. Most rifle bullets these days are spitzers, so they'd fall tail-first, which would cause less drag (and give higher sectional density on impact) than would a handgun projectile falling on its' side.

Edited to add:

Of course, this only deals with bullets falling straight down, but bullets fired at an angle to something similar; cylindro-ogival bullets will fall in a nose-up position similar to a landing airplane. Spitzers, at all but the most extreme ranges (for their respective loadings, that is) fall point-foremost. I think the nose-up degradation occurs somewhere shortly past supersonic burnout, but I'm not sure; Greg probably knows.