FIG. 1 is a front view of a multiple slot expanded diameter paintball marker barrel showing my new design; FIG. 2 is a left side view thereof; FIG. 3 is a back view thereof; FIG. 4 is a top view thereof; FIG. 5 is a right view thereof; FIG. 6 is a back view thereof; and, FIG. 7 is an isometric view thereof.