The carriage allowed transportation of the weapon over short distances with the speed of 5–8 km/h (3–5 mph), for longer distances the barrel was removed from the carriage and transported separately on a special wheeled cart, the Br-10, a speed of 25 km/h (16 mph) was possible with the barrel removed.

The aging guns and their insufficient numbers (the M1914/15 at less than half of what was mandated in the 1941 mobilization plans, 66 pieces) meant that new models were required, including 280mm-caliber ones.

However, despite the B-33 showing better shell grouping, higher rate of fire and smaller dimensions, the Br-5 was accepted into service as the 280 mm mortar model 1939, with the first order for production being issued before field tests ended.

The first order for eight pieces was placed with the Barrikady factory in May 1937, although this was subsequently reduced to two in recognition of the immaturity of the system.

Four Br-5 mortars were deployed to Finland with the 40th Separate Artillery Battalion, where they were used to destroy heavily armoured bunkers and pillboxes during the battles along the Mannerheim Line.

[3][5] Information about the employment of the Br-5 mortar during the Great Patriotic War is scarce; their deployment was heavily classified as it was generally indicative of a major attack.

The high-explosive shells were all remaining pre-revolution stocks of 280 mm Schneider M1914/15 ammunition, whilst the anti-concrete was created for the Br-5.

[9] A Br-5 mortar on the original tracked carriage is kept at the Military Historical Museum of Artillery, Engineers and Signal Corps in Saint Petersburg.