Anyone up for the chicken or the egg argument??
If you're rifle is sighted for a specific distance and you want to see where the shots land at half the distance, your aim is going to be at a fixed point and you can see where you/your rifle/ammo is going to hit.
The bullseye is only a convienient aiming point. After I get used to what my rifle/load combination does, I'll adjust my aiming point at said range so the bullets will strike the bullseye. I do the same thing in the field on game, whatever it might be.
I too, have had those who advise me to adjust my sights to "hit the bullseye" at a specific range, but those helpful folks assume it is what I am trying to do.
Not necessarily, and I don't mind the advice, either.
If I am trying to learn what my weapon will do at various ranges in the game field, I go with the assumption that my quarry is not going to hold still for that perfect shot while I'm dialing this or adjusting that.
I don't expect bambi to run over to a point where they are exactly 200 yards or so from the muzzle so I can place the shot "in the bullseye". It's called "holdover" or maybe "holdunder".
Your weapon has to be able to hit with some kind of consistancy in order to line everything up, the ammunition has to make the bullet leave the barrel the same way with every shot, and more importantly, the shooter has to be capable of shooting the weapon consistently in order to make it all happen.
If you take away anything out of that combination, you are not likely going to hit what you are aiming at, whether or not its the bullseye.