A method of reducing the friction between the wall(s) of a mold and the outer wall(s) of a metal container fitting snugly in the mold and containing a metal ammine complex salt which is uniaxially compacted within the container, comprises a) treating or covering the inner wall(s) of the container with a lubricant before the metal ammine salt is filled into the container, or b) mixing a solid lubricant with the metal ammine salt to be filled into the container is, or c) treating or covering a gas-permeable enclosure made of a flexible material and wrapped around the solid metal ammine salt with a lubricant before the solid metal ammine salt wrapped into the envelope is filled into the container, or a combination of a) and b) or a) and c). A lubricated container and a lubricated enclosure each containing a metal ammine salt is also disclosed.