Using planar-plate impact technique in combination with a velocity interferometer VISAR dynamic properties of Armco iron at sample temperatures of 290 K < T < 1050 K have been determined. At temperatures above 800 K the ot-y phase transition has been observed, when pressure stresses exceeding 9 GPa were applied. Softly recovered samples have been examined by means of optical and SEM microscopy. At temperatures and stress levels sufficient for the ct-y, ct-e and y-e phase transition, the samples show considerable changes in the structural condition. The samples used for the planar-plate-impact tests may be regarded as very simple structure elements. The experimental results will show, that although the structure is very simple, surprising results may arise from the alternating effects of shape, size and material properties.