A rimless cartridge cylinder assembly is used for adapting revolvers which typically require the use of rimmed cartridges to accept rimless cartridges. The assembly includes an extractor mechanism having an extractor rod extending axially through a center passage provided in a cylinder having chambers adapted to receive cartridges. The extractor mechanism has an axially extendable extractor head assembly disposed at a cartridge loading end of the cylinder. The head assembly includes a plurality of spring biased projections housed therein which extend radially into engagement with corresponding grooves in rimless cartridges as they are loaded into each chamber. After discharge, rearward displacement of the head assembly allows the engaged projections to remove the spent cartridges from each chamber. Utilizing the rimless cartridge cylinder assembly, rimless cartridges typically used only with automatic hand guns can be loaded and fired in a revolver with long term reliably.