Abstract: A primer feed mechanism for automatically feeding unfired primers to, and extracting fired primers from, an artillery piece. A magazine having a rotatable cylindrical drum carrying a plurality of primer cartridges is detachably mounted adjacent the breach block of an artillery piece. A user actuable release handle controls movement of a reciprocable mounted camplate. Movement of the camplate in one direction indexes the rotatable drum to align a fresh primer cartridge with the firing chamber of the artillery piece. Such movement of the camplate also drives a rearwardly positioned bolt toward the breach block of the artillery piece thereby driving the unfired primer cartridge into the firing chamber. Movement of the camplate in the opposite direction causes the bolt to extract the fired primer cartridge from the firing chamber and back into the magazine drum.