John Newman
The Bunker Group
Actually there is a bit more to it beyond what you wrote above (have a re-read of the spec sheet).It is actually a bit more complicated than that even. Here is the latest LockMart C-130J (& variants) brochure that I came across, it is about 32 pages.
The C-130J-30 is ~15 ft/4.6 m longer, so there is more volume available for cargo than a KC-130J, but it also has a higher empty weight and lower max cargo weight, albeit not by much (~300 lbs less).
Therefore, which Super Herc can carry 'more' depends on whether that 'more' is space or weight.
As an aside, it appears that there are variants of the aerial refueler that can provide a rapid ground refuel capability to support vehicles. That could open up some interesting opportunities for forward operating bases, expeditionary ops and potentially even HADR, in addition to the 'normal' support of fixed- and rotary-wing AAR.
A C-130J-30 doesn’t normal carry the two underwing fuel tanks of previous models (it can but doesn’t come standard).
A KC-130J has both the two underwing fuel tanks of previous models, plus the two outboard refuelling pods.
A few years ago the RAAF started re-fitting those ‘missing’ fuel tanks:
RAAF C-130Js to fit external tanks | ADBR
UPDATED 16:20 19/11/18 The RAAF’s C-130J Hercules operated by Richmond-based 37SQN will have external fuel tanks fitted, initially to two of their aircraft. Previously fitted between the engines on each…
adbr.com.au