A modified elongate ammunition magazine, the magazine being modified by modifying an elongate, single plane magazine by removing its end cap so as to provide an elongate modified magazine having an upper end for attaching to said magazine well of a firearm, a lower end, and a through passageway therebetween, and a clip leg base attached thereto and also attachable to a high capacity ammunition magazine housing, the clip leg base configured such that when it is attached to said modified magazine to construct a feed clip assembly, and when the clip leg base is also attached to a high capacity magazine, and when the upper end of the modified magazine is installed into a firearm, an ammunition passageway is defined from an ammunition outlet of a high capacity ammunition magazine housing, through the modified magazine, and to a firearm. Also provided is a last linked assembly including a loose or spreadable link.