As all Space Marines are Unnarmed Masters (1d10 + SB damage, non-Primitive) and Improvised Weapons do 1d10-2 + SB damage, Primitive & unbalanced, is there ever a reason why a space marine might use an Improvised weapon?
It also seems odd that leverage and momentum doesnt come into it and swinging a ceramal chair over someones head does less damage than punching them (note that unnarmed master doesnt assume the space marine is amoured).
SJE