A baler (70) for manufacturing bales of harvested crop material comprises a bale chamber (80) comprising a first part (50) where a plunger (13) can make a reciprocating movement, and a second part (51) which cannot be reached by the reciprocating plunger (13). The second part (51) has a varying cross section along the length direction (110) of the bale chamber (80), whereby the rate of change of the cross sections is different on at least three distinct positions along the length direction of the second part (51) of the bale chamber (80).
