In 1944, when he was 17, he joined the British army after obtaining a forged document from the Mukhtar of Petah Tikva. After his demobilization he joined the Irgun, starting out in the propaganda unit. He was then sent on an commanders course, and it was while attending this that he was chosen for the mission of attacking the railway station in Jerusalem (October 30, 1946). After the explosion he was wounded and caught by the British police. He was brought to the Government Hospital, were his arm was cut of. Feinstein was tried by a military court and was sentenced to death by hanging.
On Monday, April 21, 1947, half an hour before the execution of Feinstein and his friend Barazani took place, two explosions were heard from the cell in the Jerusalem prison: Moshe Barazani and Meir Feinstein stood embraced. The grenades were held between them, at the height of their hearts. Meir lit a cigarette, with which he ignited the fuses that Moshe held, and they died together as heroes.