RE: Info on a 12 ga. slug gun with a rifled barrel ??
Sight in your gun in the 40-50 yd range.
A 12ga has such broad frontal sectional density that these power houses really do not buck the wind very well and may give you false reading at the 100yd mark because of drift.
The maximun I would shoot a 12ga slug is 125yds, under near perfect conditions.
Good Luck