Probably not.
8" @100yds, is that with a scope? off a bench? Your gun will do much better than that. Unless of course your rings/bases are loose or your scope is busted. I shoot the hardcasts into a ragged hole @50 with 60g's of 777 ffg. Start from scratch and re-check everything, and like it was said if that pin is a snug fit look for problems elsewhere. Loose fore-end screws, proper seating depth, not mashing the bullet into place, etc... etc...