SO-152 (СО-152) is a Soviet 152.4 mm self-propelled gun developed in 1968. The SO-152 (Russian: СО-152) is a Soviet 152.4 mm self-propelled gun developed in 1968, as a response to the American 155 mm M109 howitzer. Development began in 1967, according to the Resolution of the Council of Ministers of the Soviet Union from July 4, ...