R2nailler
Head spacing is about the depth of the chamber reaming, specifically of the case shoulder, with respect to the bolt face. It is basically the "slop" between a properly sized round and the bolt face. It has nothing to do with the cant, position or condition of the front site.
However, if the front sight is missaligned, you wil find a problem when zeroing the rifle at different ranges - it will be off right to left. You'll be able to zero it at a specific distance, but as you move from that distance, you'll have an error. Typically the best thing to do then is sight the rifle left to right at as far a distance as possible as this will minimize the error.
Example:
Rifle with an 18" sight radius (distance from rear sight to front sight) has the front sight 0.025" left off center. If the weapon is then zeroed at 25 yards, the rear sight is moved further off center to correct for the right to left error and the line of aim is drifting left to right. It's off by a 1/10" at 100 yards or a half inch at 500 yards. If you then re-zero at 500 yards, you'll be about 0.005" of an inch left at 100 yards.