A self-adjusting tool for chamfering an end of a cylinder includes a plurality of legs. A distal segment of each of the legs extends in a forward direction of the tool and is placeable about the end of the cylinder. A central body has a rotatable shaft and a mechanism that is operable by rotation of the shaft about a shaft axis. The mechanism is operable to retract the legs inward in tandem toward the cylinder and to rotate the legs about the shaft axis when further retraction of the legs is blocked by contact with the cylinder. One or a plurality of chamfering blades are each attached to one of the legs. A cutting edge of each blade is oriented diagonally forward and inward.

A method and apparatus for sizing ammunition cartridge cases includes a cartridge case trimmer including a cylindrical housing, a mandrel detachably coupled to a longitudinally-oriented opening formed in a first side of the cylindrical housing, the mandrel having a first end including a cutting tool disposed in a slot on the first end and comprising one or more notched cutting surfaces, the mandrel having a second end opposing the first end, the second end protruding from the first side of the cylindrical housing and sized to be received in a chuck, a bearing disposed within the cylindrical housing adjacent to a second side of the cylindrical housing, and an insert comprising a tapered region disposed in an inside diameter of an inner ring of the bearing.