Single screw extruders with a grooved feeding section can show a forced conveying of solid particles leading to high specific throughputs. The requirements for such a forced conveying were discussed in literature, and models to describe them were presented. Actual visual ob-servations of the processes inside the feeding zone are difficult due to high pressures and thus are scarce to find. Therefore this study deals with a simplified experimental setup based on an unwound flat screw channel implementing a kinematic reversal. It allows the visual observation of the solid movements and the measurement of the force to move the movable wall of the setup. It features variable screw channel heights, groove geometries and different bulk materials (PE, PP, PS). This setup allows insight into the actual formation of the particles in the groove and the interaction of the particles in the channel with those in the groove. The experiments show particles agglomerating into wedges above the groove for certain configurations. These wedges support the movement of the particles towards the end of the channel. The experimental setup allows the material to be compressed towards the end of the channel which leads to a pressure build up in the channel. For each combination of channel height, groove geometry and material type a maximum pressure level exists which can be achieved until the wedge collapses. Relative to material kind, dimensions and shape, varying conditions are observed. Accordingly, particular material characteristics are identified to reflect the difference in solid conveying. In this study a modeling approach based on the Hertzian theory for contact stresses is pre-sented to calculate this maximum pressure level for different configurations of bulk materials, channel height and groove geometry.