TB - yeah, from what I heard the hercs were at 40ft. Inverted. And the crew were naked. On goggs. With the lens caps on.
Still, it's a good question and definitely worth asking.
Cock.
QDM etc - it's a regular thing to practice approaches whilst out training. The approach is flown configured at 250ft, 125kts
If the airfield is capable of accepting a C130, has ATC (and various other criteria) then the approach to go around is flown to a lower height. The idea of using grass strips/disused airfields is to practice visually acquiring and positioning for Tactical landing strips (TLZs) - grass, dirt etc.