An ambidextrous magazine catch mechanism for a pistol includes a button in the pistol frame. The first chamber is for housing a motor for assisting the steering force. The apparatus for producing a solid fuel adopts the method. The data collected are transmitted to a control station. The processor correlates the received sinusoidal signal to a mathematical reference sinusoidal signal, and determines a specific cycle and a specific phase as a time of flight measurement point based on the correlation. As a result, even if there is a difference in the distance between the sensors, the first and second reading start points D and F will still be a first margin length L1 before the image reading positions A and B of the contact image sensors 21 and 22.