A computation device for computing the position of a tool for cutting a ridge line formed by a cylinder surface and a peripheral wall surface forming a through-hole passing through an article being processed in the shape of a column, the computation device computing the position on the basis of a first foundation vector and a second foundation vector in a plane that is perpendicular to a tangent line of the ridge line, data being processed, an ellipse formed by the plane and the column, a prescribed process width, the radius of the tool, and the angle of a distal-end corner of the tool.

A skeletonized bolt carrier for an AK rifle is provided. The bolt carrier features a skeletonized operating rod to reduce overall weight while maintaining structural integrity. The bolt carrier also features side indents cut out of both sides of the base block which further reduce weight. The reduced weight of the bolt carrier enables lower gas consumption when firing, resulting in less recoil and less associated muzzle rise, leading to improved accuracy especially when multiple rounds are fired consecutively.

A skeletonized bolt carrier for an AK rifle is provided. The bolt carrier features a skeletonized operating rod to reduce overall weight while maintaining structural integrity. The bolt carrier also features side indents cut out of both sides of the base block which further reduce weight. The reduced weight of the bolt carrier enables lower gas consumption when firing, resulting in less recoil and less associated muzzle rise, leading to improved accuracy especially when multiple rounds are fired consecutively.