Weale (pictured), the world number 22, went into the decisive run/shoot ranked tenth but slipped to 19th while team-mate Jamie Cooke, the world junior champion, was six places further back.
"The competition was very unforgiving," admitted Great Britain performance director Jan Bartu.
"The field is so equal now and there are so many good athletes."
Benedetti climbed from seventh in the run/shoot to take gold while Russia's Andrei Moiseev and Hungary's Peter Tibolya completed the podium.
Britain's other Olympic hopefuls will compete at the fourth World Cup in Russia next week after which Bartu and his team will finalise their selections for the World Championships in Rome, the next opportunity to seal the London 2012 selection standard