PURPOSE: To provide the subject unit capable of assuredly feeding a stock in a hopper into a barrel and also of preventing development of bridge phenomena in the hopper.

CONSTITUTION: A hopper 35 mounted on a 1st barrel 31 is furnished with vertically reciprocating two stock-forcing plates 95 to assuredly feed a stock in the hopper 35 into the shell 31a of the 1st barrel 31. Because the stock-forcing plates 95 are provided over the whole range of the width direction of the opening 36 of the hopper 35 in the direction of conveying the stock, development of bridge phenomena can be prevented over the whole range of the hopper 35. Besides, as the stock-conveying plates 95 are plurally disposed in the hopper 35, such bridge phenomena can further be assuredly prevented; even in case such phenomena occur, the stock is forcedly allowed to go to pieces.