‘Normal stooging around speed, Mr Sulu’. ‘Aye, Cap’n’
There’s no such thing really. Working (as opposed to hobby) aircraft generally travel as fast as is possible, safe and comfortable for the specific circumstances they’re employed in. So for a Hercules in normal high level cruise, the power is set to Max Continuous and the speed is whatever it will be (normally about 330-340kts TAS). At lower levels, the speed will be standardised for different purposes. In a climb to a high-level cruise (above say FL200), a C130 normally uses a reducing IAS technique which will start at 210kts and reduce with altitude. However, for a shorter flight that doesn’t justify a high level cruise, we’d fly at Vno, which is 270kts. However at low level (and in turbulence) 270kts is bloody uncomfortable and means your troops aren’t going to be fit to fight when they get to where you’re taking them, so the normal low level cruise speed is 210kts.
Similarly, for normal operations the C130 is operated to Performance A criteria, which demand that the aircraft can safely fly on three (and sometimes fewer) engines. So landing and takeoff speeds are calculated with reference to Vmcg and Vmca (minimum control speeds on the ground and in the air at the point of losing the critical engine). Those criteria and speeds are totally inappropriate for maximum performance tactical operations, so they are thrown out the window when necessary to achieve a military task - and the extra risk is accepted.
Edit: the point is, working aircraft (military or civil) are flown at their maximum legal capabilities most of the time, as that’s where they’re most efficient. Legalities may demand slower speeds in specific circumstances - for instance all traffic is limited to 250kts below 10,000’ unless safety demands they must fly faster. There are exceptions for military traffic in specific circumstances, but speed limits still apply even then. The C130 generally isn’t going to break any military speed limits!
