A rivet pin shooting technique was attempted to investigate the effect of operational factors (cooling intensity by water spraying, superheat of steel and withdrawal rate) on the structure of solidifying front and case morphology. In this technique, steel pins were shot from Drivit gun into moving continuously case slabs. From the results obtained by applying the new technique above mensioned, solidification rate was determined and the effects of cooling intensity by water spraying on the solidification were elucidated. The measurement of secondary arm spacings of dedrites indicated that solidification rate was accelerated at the bottom end of liquid pool.