Free: Contests & Raffles.
Possibly a bad heat-treated batch of springs? Too brittle... Sounds like it is the same (more or less) type break each time? Can you find a different manufacturer/brand spring that will fit and give it a try and see if it holds?
The bigger question is were you wearing your helmet?
You should post this on Trapperman. Might get some ideas from other parts of the country.
I spoke with Mike Morris today and I asked him about this. He said he had problems with breaking springs in Koros, never Hancocks. He said the key thing was to never snap the trap out of the water or empty. Dry snapping Koros breaks the spring he thought about 50% of the time.Passing his advise along.