Gas distribution apparatuses, e.g., showerheads, comprise passages having a first conical bore section, a small bore section, and a second conical bore section. The first conical bore sections comprise a first non-perpendicular wall angle relative to a back surface of a faceplate. The second conical bore sections comprise a second non-perpendicular angle to a front surface of the faceplate. The conical sections including non-perpendicular angles are effective to mitigate and/or eliminate changes in flow parameters through the passages after bead blast processes.