Hi 4-star
There is a direction valve shown in the second Pic down that is located near the tool head spring anchor#57 that reverses the air pressure to the pneumatic
cylinder and the bullet holder tries to retract away from the machine but is cought on a step , when the tool head comes down it pushes the bullet holder down and off the step allowing it to retract and pick up another bullet.
Clear as a bell,, Right.
Good Shooting
Lindy