Line 3 quart bowl or mold with plastic wrap leaving overhang. Chill in freezer about 30 minutes. Spoon softened pistachio ice cream into chilled bowl, pressing with back of spoon into even 1" layer, to line bowl completely. Freeze, covered with foil or plastic wrap about 1 1/2 hours or until firm.
Remove bowl from freezer, spoon lemon sherbet into bowl over ice cream; press into even layer about 1/2" thick to cover ice cream completely. Cover again and freeze about 1 hour until sherbet is completely firm.
Stir raspberry sherbet in small bowl to soften slightly; stir in chocolate chips. Spoon sherbet into center of ice cream lined bowl to fill completely. Smooth top of all 3 layers. Freeze, covered, at least 3 hours or overnight. Thirty minutes before serving time, chill round serving platter in freezer. Insert end of metal spatula between plastic wrap and bowl to loosen. Invert bombe onto chilled platter, peel off plastic wrap. For serving, use sharp knife to cut bombe in half and then into slices. Makes 10 to 12 servings. Looks like a watermelon when sliced.