A fuel injector for controlling fuel flow to an internal combustion engine and a method of setting dynamic calibration for the fuel injector. The shoulder tread regions are defined by a repeating pattern of two or more distinct shoulder tread elements and the center tread region is defined by a repeating pattern of two or more distinct center tread elements. Thus the roller becomes detached from the frame and the follower cannot actuate its designated valve. The live cartridge has concentric inner and outer tubes defining a toroidal explosive charge-containing chamber therebetween and a light passage through the innermost tube, and a bullet having a passage therethrough allowing light to pass through the live cartridge assembly when placed in the firearm chamber.