Yeah, I have to agree with Bubbler on this one...The shooter matters of course, but so does the barrel and slugs. Choked barrels generally do not shoot slugs as well as non choked barrel unless the choked barrel is made especially for slugs like the FX slug barrels or you get lucky. It's pretty uncommon to just grab a slug and have it shoot in your gun. You generally have to try many, at various velocities to see what you can get to work. Even then, sub moa groups are not easily achieved. People have had success with slugs at various velocities but again, in general most slugs perform best at higher velocities since they are spin stabilized. I've had the best luck with most of the slugs I've tested at between 920-980fps.
Stoti