A safety magazine allows training rounds to be fired while preventing the firing of live rounds. The magazine has front and rear walls, whereby the distance between the front wall and the rear wall is less than the length of a standard 5.56×45 mm NATO cartridge. The magazine has an alignment rib projecting from the rear wall that is adapted for insertion into an alignment groove formed in a rear end wall of a standard M16 style magazine well. The magazine has a spacer projecting laterally from the sides of said alignment rib and that is located between the rear wall of the magazine and the rear face of the alignment rib. The spacer is adapted to engage the rear end wall of the standard M16 style magazine well for spacing the rear wall of the safety magazine away from the rear end wall of the magazine well.