I agree with butch - 152mm Gun-Howitzer M1937 (ML-20)
Country: USSR
Caliber: 152.4mm (6 in)
Weight: 7128kg (7 tons)
Gun Length: 4.42m
Elevation: -2 to +65 degrees
Traverse: 58 degrees
Shell type/weight: HE; 43.56kg (96lb)
Muzzle Velocity: 655m/sec (2150ft/sec)
Maximum range: 17,265m (18,880yds)