by Krypos » 5 Aug 2006 23:25
perhaps the spring differences are what make them harder or easier. more force or less force on each pin. or perhaps one is dirtier than the others, that too can account for one lock being harder to pick than the others as well. or perhaps just the very small variations and tolerances in construction, the key would still work, but it might makle picking much different.
all i can say is to treat each lock like they are one of a kind and try to pick each one like it is new.