In 1937, F. F. Petrov and his design team at the "Motovilikha Ordnance Plant" started work on a new design, the M-10. Technical papers were submitted to the Artillery Directorate on 1 August 1937 and on 2 November the first prototype was completed. Ground trials (19–25 October 1938) featured two pieces: No. 302 (L/25 barrel with constant rifling) and No. 303 (L/20 barrel with progressive rifling). The No. 303 was found to be superior. The trials also revealed numerous defects in the gun construction: the howitzer suffered from insufficient upper carriage strength, leaks in the recoil buffer, unreliable suspension etc. For army tests early in 1939, an improved design with a longer barrel was presented. Another series of army tests followed from 22 December 1939 to 10 January 1940, but even before it started—on 29 September 1939—the gun was adopted as 152 mm divisional howitzer model 1938. Later, the word "divisional" was removed from the designation.