Hydraulic muscles only give 20 str. With sledgehammer’s 40, it still leaves 40 strength to gain.
Even assuming a 20 strength start, insanely strong (+7), active adrenaline (+5), +2 CBM, active jet (+1), active stimpack (+1), meth (+1), you’d need almost 600 morale to get the ability to bash solid rocks with a legit character.
Do you have an old character buffed with granades or did you figure some other exploit?