On 25 September 1857, at Lucknow, during the Indian Mutiny, troops penetrated into the city, and Captain Olpherts charged on horseback with the 90th Regiment. They captured two guns in the face of very heavy fire. Afterwards, he returned under severe fire of musketry to bring up limbers and horses to carry off the captured ordnance.
At the outbreak of the Mutiny, as he was a daring and able officer, he earned the nickname "Hellfire Jack" although he was also regarded as being somewhat eccentric. He ended his army career as Colonel-Commandant of the Royal Artillery.