slugs for this gun i am unsure, i bought it for my wife for upland bird hunting, the biggest plus for the 870 (i have owned four) is the will never let you down from a function standpoint, if i were limited to slugs for large game i would go with a 12ga., as far as bird shot, never have i found anything that would not cycle thru any of the 870's we have owned, great gun, great design, and very versitile, but i have never used 20ga. slugs. i'm sure there are some here that have, i'll leave that to them, but as far as the 870, you can't go wrong

good luck and good shooting, keith