The effect of the grinding chamber length and the grinding media diameter in a Spex 8000M mixer mill was reported earlier [1]. Now a modification of the grinding chamber shape was investigated. The results presented are based on DEM (discrete element method) simulations performed for the same mass of grinding media in all cases. It was found that the rounded end caps of the grinding chamber gave higher collisional intensities of the grinding media compared to the flat end caps. The collision intensity can be maximized by adjusting the roundness of the end caps. For end cap curvatures of R/3 and R/4 (R is the radius of the grinding chamber), along the horizontal axis results in the highest intensity collisions compared to other cases studied. The maximum increase in the grinding media collision intensity in modified end caps was observed to be about 75% for one particular grinding media diameter.