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In February 1943, the design bureau of Factory #172 (headed by M. Tzirulnikov) was developing the 76.2 mm Regimental Gun OB-25 Model 1943. The gun carriage was borrowed from the 45 mm Antitank Cannon M42 Model 1942.
The very first experimental gun was manufactured in Factory #172. From 18 to 26 June 1943, the gun was tested on the Gorokhovets proving grounds. The gun fired 157 times, and the trials revealed some serious drawbacks including low accuracy and poor performance of the recoil brake. The trials were cancelled, and the gun was returned to the factory for further improvements.
At the end of July 1943, four improved guns were sent for trials at the front. The guns passed the trials successfully, and on September 4, 1943, the gun was accepted for service, and it was soon put into mass production.
The gun had the piston breech-block borrowed from the 76 mm Regimental Cannon Model 1927, a hydraulic recoil brake, and the reflexive mechanism consisted of four springs. Its elevation mechanism had one sector. The gun had either spoked wheels ZIK-1 or solid wheels GAZ-AA. The limber was taken from the 45 mm antitank gun and could accept 3 x 8 = 24 rounds. The cannon could not accept ammunition from any other gun. Its cartridge case weighed 0.89 kg.
Despite its light weight and good maneuverability, in general, the OB-25 was an unsuccessful gun due to its low muzzle velocity and absence of HEAT ammunition which made the gun almost useless against armored targets. After the end of the war it was removed from service.
In 1944, the OKB-172 had developed the 76.2 mm Regimental Cannon BL-11 with a wedged breech-block. One experimental gun was built and tested, but it wasn't accepted for service and further work was cancelled.