A
rim is an external
flange that is machined, cast, molded, stamped or pressed around the bottom of a
firearms cartridge. Thus, rimmed cartridges are sometimes called "flanged" cartridges. Almost all cartridges feature an extractor or headspacing rim, in spite of the fact that some cartridges are known as "rimless cartridges". The rim may serve a number of purposes, including providing a lip for the
extractor to engage, and sometimes serving to
headspace the cartridge