[2] In 2010, Kruglov had won a gold medal for the 10 m air rifle at the European Shooting Championships in Meråker, Norway, and eventually captured the bronze at the ISSF World Cup in Fort Benning, Georgia, United States.

[3] He is also a member of CSA Pomoriye and is coached and trained by Oleg Seleznev.

[1] Kruglov represented Russia at the 2008 Summer Olympics in Beijing, where he competed in the men's 10 m air rifle, along with his teammate Konstantin Prikhodtchenko.

He finished only in eighth place by seven tenths of a point (0.7) behind Serbia's Stevan Pletikosić, for a total score of 697 targets (595 in the preliminary rounds and 102 in the final).

[4][5] In 2013 Sergey started working for the Russian National Team, doubling his efforts as a competitive shooter.