Gossner had five misses on the shooting range in the pouring rain but still had enough speed to edge out Gabriela Soukalova by 0.7 seconds.
It was another perfect performance on the shooting range from Soukalova: she has hit 30 targets from 30 this weekend after taking her first World Cup win in Friday's sprint, with Gossner settling for second in that race.
Gossner came home in a time of 31:47.8 minutes with Marie Dorin Habert of France settling for third.
"I saw during the last round of shooting that they had made no mistakes," said Gossner.
"So I thought that I must give everything again and then see what I ended up with."
Norway’s Tora Berger, the Olympic pursuit champion, struggled in Slovenia and came home in ninth while former World Cup champion Kaisa Makarainen was 19th after seven misses on the range.