An automatic primer feed mechanism for use with a carrier assembly of a large caliber artillery piece, which includes mechanical assemblies for automatic primer loading after full breech closure and allows for spent primer cartridges to be extracted before opening of the breech to maximize safety, thereby allowing the gun crew to perform artillery piece misfire, sticker and check fire operations before the breech is opened. The mechanism includes a body member that mounts the automatic feed mechanism to the carrier of the artillery piece so as to interface with the carrier to position the mechanism on one side of the breech of the artillery piece. The body member includes a cam surface member, which provides a path for movement of an injection arm member. The tray member has guide rails for engagement with the body, which slides in relation thereto. A magazine containing a plurality of primer cartridges, which inserts in a receiver channel located in the tray member. The mechanism provides improved safety wherein live primers stored in a magazine are at a distance from the firing chamber hole that prevents flame from reaching a live charge before a fresh primer is injected therein.