A realistic range with full fuel is about 500 - 600nm. You can go
further with a very economy power setting, but somebody's bladder won't
last as long as the fuel.

As with most light aircraft, with full fuel, six occupants, and the
usual baggage, you will be overgross at takeoff.

Best regards,

Steve Robertson
Former Piper employee and Seneca III pilot

Mark wrote:

Can anybody tell me what a realistic cruising range is for a Seneca
III with long range tanks a a full load (i.e. six people including
pilot)?