what you guys are referring to (over the shoulder) raises a similar issue, except horizontally instead of vertically; to my knowledge, roblox and other games that do it have the bullets always fly towards what you're aiming, instead of towards your look vector
edit: though, this makes me wonder; in blockland, bullets are spawned from the gun, not your face, right? so how come that when you're aiming at a target, your bullets actually hit it, instead of as far away from it as the gun is from your face?