A shell feeding system for a top loading shotgun in one embodiment includes a barrel, receiver, and a magazine. The magazine includes a cavity configured to receive a plurality of ammunition shells in stacked end-to-end relationship. The magazine is positioned above the barrel and extends forward from the receiver. Shell guide grooves are formed by internal surfaces in the receiver which engage and guide each shell in a feed pathway towards the lower part of the receiver for chambering. A portion of the guide grooves may be arcuately shaped to rotate and reposition the shell for loading by the bolt into the chamber. In one embodiment, the receiver and magazine may be formed as a unitary integral structure formed as either a single piece or in half sections coupled together.