Abstract: A method and apparatus for severing a length of shirred casing from a length of unshirred casing utilizes a mandrel onto which an unshirred casing is introduced. A fluid is injected between the casing and the mandrel. The casing is shirred into tight overlays to provide a length of shirred casing. This length of shirred casing and the yet unshirred casing are engaged to displace them relative to and sever them from each other. Prior to severence, the casing is circumferentially weakened by thermal partial decomposition of the casing or by at least partial penetration with a weakening tool that does not engage the mandrel.