The invention relates to hydroxamic and carboxylic acid derivatives. The system includes a grip, such as a corrugated plastic tube, attached to a microphone and wedged into the instrument sound bole to be held in place through frictional engagement. A cutting force estimator is provided for estimating the magnitude of at least one component force of a principle force, a radial force and a feed force in a cutting force which the tool applies to a work to be processed. 80 and F32 having a value of at least 1. The invention further relates to a system casing for such a stock and a repeating rifle with such a system casing and stock.