The intimation in ZH875's post is that the canopy gun just lifted the front of the canopy into the airflow, which then completed the task. Not so. The canopy gun was positioned immediately behing the pilots - it did 'lift the front of the canopy' but was big enough, with a substantial cartridge, to blow the canopy clear of the ac without airflow assistance. The action of the pilots, in pulling the jettison levers aft, unlocked the front canopy locks.