stainless steel guitar strings and rated tensions That site also contains a link to "loop end banjo strings" which could be used to make a snare with since the loop is integrated into the end of the string for closing the snare. with tensions of approximately 25 - 30 pounds should be sufficient to snare most varmint size critters. The snapped strings experienced during playing must be due to having the string under 25# of tuning tension and then plucking them in such a way as to exceed their tensile strength. Then again a reasonably excited teenage guitar player could easily exert more than 100 pounds strain on the string (much more than a squirrel or even a beaver)

piano wire can be ordered here These folks make metal carbon steel piano wire in various diameters