The energy-harvesting behaviors of a ring-shaped PZT-5A element exposed to gunfire shock are investigated for military applications such as an in-flight power source for electronic fuze. A laboratory test using a pneumatic shock machine up to 3000 g's and a gunfire test accompanied by the acceleration of 65,000 g's have been performed. The PZT-5A element subjected to gunfire shock has worked in its strong-depolarization region, thereby generating the electric energy whose quantity is about 140.4 times larger than that measured in its linear operation region. The experimental studies on the PZT-5A element under dynamic load have demonstrated three physico-electric characteristics: the dependence of piezoelectric constant on load-rate, the shock-aging of piezoelectric effect, and the dependence of energy-transfer efficiency on the change in normalized impulse.