Water cannon Range modifier

Normally (ie. for melee/range/magic damage), the critical modifier is calculated solely from Max Damage (rather than a random roll between min and max) and added to a non-crit roll. Since jpwiki hadn't accounted for this in their formula, and I hadn't tested it specifically with water cannon myself, I didn't see fit to change it, however it would explain the high minimum crit damage that you're seeing.