A mixing machine barrel has parallel interconnected bores of a first diameter with axially parallel shafts driven at the same speed and in the same direction of rotation extending therein. Mixer members on the shafts are shaped to co-wipe and also wipe the interior of the barrel. A barrel section communicates with the barrel and has interconnected bores of greater diameter which include interconnected transition bores of progressively changing diameter. Blades extend at an angle from the shafts through the transition bores and are configured to wipe one another over their length, and the interconnected bores of the barrel section over their length.