On a 1377, the hammer is cocked rearward against a spring and held in place by the sear. The pressurized valve is completely separate from the hammer - nothing but air in between. The only interaction between the two is when the hammer is released to move forward and hit the valve pin.(Pic borrowed from here - https://www.crosman-air-pistol-owners-forum.com/board/index.php?topic=5631.0)