Elevator, bowl feeder and linear transfer load 2 barrels to the ready position at the same time. Gripper will transfer the 2 barrels into the fixture of station 1. Station 2 will do the orienting work to make the barrels in right position. Then lock the 2 barrels at the right position. Each station will have a twin-head reaming unit. Each reaming unit will only ream one pinhole on the barrel. Totally, there are 5 or 6 reaming unit working at the same time but on different pinhole. After finishing the reaming work, the gripper will unload the barrels to the slide.