Bubnov was born in Nizhny Novgorod and graduated from the Marine Engineering College in Kronstadt in 1891.

He initially joined the Admiralty Shipyard in Saint Petersburg and worked as a constructor on the battleship Poltava.

He was commissioned into the Navy in 1907 and was head of the Admiralty test tank between 1908 and 1914.

Bubnov was promoted to major general in the Corps of Naval Engineers in 1912.

Between 1912 and 1917, he was a consultant to the Baltic Works in Saint Petersburg and the Nobel & Lessner shipyard[1] in Reval.