A chuck-knockout assembly for seaming a can end onto a can body to form a seamed container is disclosed. The chuck-knockout assembly may include an upper chuck body and a lower chuck body. The upper chuck body may include a first drive surface and may be rotatably coupled to a seaming machine frame. The lower chuck body may include a second drive surface and may be longitudinally moveable relative to the upper chuck body. The second drive surface may be configured to engage a periphery of the can end during seaming and disengagement of the container.