In figure 4-22 (c), when the breechblock is held in the open position with the operating crank pin engaged in the cradle cam, the closing springs inside the operating crank are under tension.
In figure 4-22 (b), during counterrecoil, the operating crank pins enter the cam grooves on the underside of the cradle cam. When the breechblock is held in the open position with the operating crank pin engaged in the cradle cam, the closing springs inside the operating crank are under tension.