have you played with any "pose running" technique drills... the "bare foot running" shoes will tend to put you on to your toes, hence the calf soreness... there are some pose running techniques that teach a slight "kissing" of your heel to ground on each strike, relieving the calves a little... and giving more shock absorbency leading to longer distances...
here is a little theory of mine, half proven, so modern running shoes provide shock absorbency, which is one of the jobs of the calf muscle, so by running and walking in supportive shoes we reduce workload on the calves, leading to less shock absorbency in our legs, thus leading to more injuries and then a greater reliance on shock absorbency of the shoe...
then add the shoes doing the work of the foot arch, and as the shoe wears, the arch support and the cushioning fail... leading to strain on both front and rear lower leg injuries... aka the myriad of problems covered by the name "shin splints"...
then add weight in the form of belt rig and/or bergens/large packs...
its a cycle that if not 100% in all cases seems to be anecdotally true in some chronically injured soldiers/operators... I've seen these problems mirrored in triathletes, getting compartment syndrome/shin splints/knee problems/back soreness when running... due to the legs being quad dominant and "good" running shoes, they then often can't do 25 body weight calf raises, but will run 5-42km off the bike...
ok soap box away... i'll end up talking piss on this for hours bahahahaha
smudge-out