a 17-month program was conducted to develop an electrochemical machining process for rifling 25mm, 7-foot-long gun barrels with gain twist rifling. using a stationary electrode approach, a process and appropriate tooling and operating parameters were developed and demonstrated by rifling two barrels each of 4340 steel, pyromet x-15 and cg-27, and one barrel each of pyromet 860 and alloy 718 dimensional and metallographic evaluations of the rifled barrels verified that this process has high potential as a production rifling technique for steel and superalloy barrels. a producibility study was conducted to predict production costs. a secondary objective of the program was to investigate the feasibility of electrochemically drilling gun barrels in the 25mm size range utilizing a conventional forward flow and a new reverse flow process. the conventional forward flow process showed that deep holes could be drilled, but dimensional control could not be maintained. the reverse flow process showed considerably more promise with improved dimensional control. (author)