[UnderseaLcpl]

What's the target? Is it moving or stationary? What type of round? What weapon?
Wind conditions? Am I upwind or downwind? Is there foliage in the way? Wind velocity/direction? Sighting mechanism? Temperature? Is it raining?

If we're talking about a rifle with 3000-3500m/s muzzle velocity over an open range, you should never need to be closer than 200m, even with iron sights, in a fair amount of wind. The bullet pretty much hits instantaneously, even if it is a low-caliber round.

As far as bows go I'd have no idea. I went bow-hunting for the first and last time when I was twelve. I spent days freezing my ass off, shifting from one location to another, and when I finally got within range of an 8-point buck, I hit him in the butt. Poor thing. I hope he got the arrow out with only a flesh wound, which would seem likely since I'm sure that my draw was pathetic at the time.

For dove I like to use my Remington 870 with just a little choke at ranges between 20 and 100m. It makes for a nice pyramidal pattern, and since you can see the pellets, leading the target isn't a big problem. You'll miss the first few times, but you get the feel for it pretty quickly. Use both eyes when accquiring and leading the target.