A method of manufacturing a liner for use in a pressure vessel includes a cold drawing process that shapes a transition zone (20b) part of an aluminum alloy liner shell (10). The transition zone (20b) links a thinner walled drum part (18) and a thicker walled end region (20a), which is at an open top of the shell. The transition zone (20b) may be shaped by the cold drawing process such that it reduces susceptibility of the shell to fracture during removal from a cold drawing press and also redistributes shell material in preparation for a subsequent process in which a threaded neck is formed from the end region (20a). This process is particularly suited to processing harder aluminum alloy materials such as AA7060 or AA7032.