[1] Competing at the 2021 European Shooting Championships in Croatia, Claussen won a silver medal in 50 m rifle 3 positions team, along with Jon-Hermann Hegg and Henrik Larsen.

Together with Jon-Hermann Hegg and Henrik Larsen, who won individual gold and silver medals, respectively, he set a new world record for teams in the qualifications with a total of 3549 points.

[8] In June 2023 Claussen competed at the 2023 European Games, where he won a bronze medal in mixed team, along with Jenny Stene.

[9] Along with Ole Martin Halvorsen and Jon-Hermann Hegg, he qualified for the finals in 50 metre rifle team, where they placed fourth, defeated by Serbia in the bronze medal match.

[10] At the 2023 ISSF World Shooting Championships in Baku, he won a gold medal in 300 m rifle prone team, along with Kim-André Lund and Odd Arne Brekne.