[Al Skierkiewicz]

Jason,
The rating is a direct result of heat rise in the contact. With larger wire, more heat is transferred away from the contact by the wire. It is essentially acting as a heatsink. Solder will only affect the heat rise if a crimp was made improperly and the wire is loose in the contact. The higher resistance will produce more heat. Dirty contacts, bent and misaligned or scratched contacts likewise will have higher heat associated with them.