if you pull on the cocking lever a third of the way and hold, the piston should retract back and ease up pressure on the loading block for you to open it. dont open it plush against the side of the breech, leave a tiny space between the tab and the breech side big enough to fit a flathead screwdriver and wedge the flathead in the space and slowly pop/pry the tab out. be careful not lose the tab lock when pulling the tab off.