Patent ID: 7735252

Claim:
A firearm magazine comprising: a housing having longitudinal sidewalls and transverse sidewalls defining a cavity for accommodating a plurality of cartridges, each longitudinal sidewall including a first portion having downward-facing chamfered surfaces projecting inwardly into the cavity at the upper portion of the housing, and including a second portion defining a chamfered surface angled downwardly from said first portion to one of the transverse sidewalls; a resilient member disposed in the cavity; a cartridge support member movably supported on the resilient member and configured for being moved downwardly into the cavity against increasing tension of the resilient member when the magazine is being loaded with cartridges, and configured such that the resilient member when under tension urges the cartridge support member and cartridges when disposed thereon to move upwardly toward an upper portion of the housing when feeding a firearm with a cartridge; and an adapter for converting a firearm magazine from multiple cartridge capacity to single cartridge capacity, the adapter being configured to be removably coupled to the upper portion of the housing so as to cover the cartridge support member of the housing, and the adapter including an additional cartridge support member, the adapter including sidewalls each having an upward-facing chamfered surface at an upper portion complementary to the downward-facing chamfered surfaces of the longitudinal sidewalls of said housing and having a downwardly depending portion at a lower portion, and the adapter also including a transverse end wall having chamfered surfaces angled upwardly from said end wall outside said sidewalls and complementary to the downwardly-angled chamfered surfaces of the second portions of the longitudinal sidewalls of said housing, the complementary chamfered surfaces of the housing and the adapter cooperating to positively engage the adapter with the housing and prevent the adapter from being moved downwardly into the housing.