Mortars Br-5 were designed to destroy especially strong concrete, reinforced concrete and armored structures; the fight against large-caliber artillery or artillery sheltered by strong structures of the enemy.
The mortar barrel is fastened, two-layer, consists of a pipe, a casing and a breech. The pipe consists of a threaded part and a chamber; in the barrel, the pipe has a thickening to balance the barrel. The grooved part has 88 grooves of constant steepness. The chamber consists of two conical and one cylindrical parts. The breech is a steel forging screwed onto the end of the casing, the breech device is generally similar to that of the B-4 howitzer. The piston bolt, of the Schneider type, locks in two strokes, is similar in design to the bolt of the B-4 howitzer, but larger in size.
Air-hydraulic recoil devices. The rollback and knurling brake cylinders are installed in couplings fixed with gougeons on the cradle. The cradle with trunnions lies in the trunnion sockets of the upper machine and is connected with its sector movably with the gear of the main shaft. Rollback brake is hydraulic. The reel is hydropneumatic. The recoil devices are motionless during rollback. Unlike the gun carriage of the B-4 howitzer and the Br-2 cannon, the recoil brake of the gun carriage of the Br-5 howitzer has keys of variable cross-section, which made it possible to rearrange the barrels.
The carriage is caterpillar, consists of an upper machine, a lower machine and a running gear. The upper machine is a riveted structure supported by three rollers on the supporting surface of the lower machine and moved by means of a rotary mechanism on the combat pin in the horizontal plane. The lower machine in the frontal part is fastened to the combat axle of circular cross-section, the ends of which are movably connected to the caterpillar track. The trunk of the lower machine has two openers - a permanent one for hard ground and a folding one for soft ground. The lower machine of the Br-5, in comparison with the early machine of the B-4 howitzer, is additionally reinforced with riveted sidewalls and a thickening of the upper sheet. The undercarriage includes a caterpillar track, a braking device, a suspension system, and a winch for turning the howitzer.
Lifting and turning mechanisms of sector type. There is a special mechanism for loading the loading system, which ensures that the barrel is quickly brought to a horizontal position. The sighting device consists of a sight, a panorama and a sight drive with a bracket. The lifting mechanism made it possible to direct the mortar in a vertical plane in the range of angles from 0 ° to + 60 °, however, it was possible to fire only at elevation angles of more than + 15 °. Horizontal guidance was possible in the ± 4 ° sector.
The loading device consists of a crane with a winch, a cocoon, a mechanism for locking the shaft to bring it to the loading angle, a rack with a tarpaulin and a slug trolley. The loading of the gun proceeded as follows: the shells are taken out of the cellar and placed on a wooden platform. The projectile, prepared for transportation to the mortar, is installed vertically. Further, the fighter rolls the shell cart to the shell at the rate and covers the shell with the help of grips. Then the projectile is placed on a cart and fixed on it, after which it is transported on a cart to the rack and placed on a tarpaulin. The rack is installed at the carriage under the crane, the cocor is lowered into the nest of the rack and the next shell lying in the rack is placed in the cocor. The mortar is brought to the loading angle, after which the shaft of the loading mechanism is locked. The cocor is hung on two hooks located on the breech of the gun barrel. After hanging the kokor, the cable is somewhat weakened, while the paws of the kokor levers release the projectile, which is sent into the barrel bore by the efforts of four fighters.
The transport of the gun over long distances is carried out separately (the barrel is separate from the gun carriage). For short distances (up to 5 km), an indivisible carriage of a gun with a retracted barrel is allowed at a speed of no more than 5-8 km / h. For transportation by mechanical traction, the gun had a front hitch. With a separate carriage, the barrel was transported on a sprung gun wheeled vehicle Br-10 at a speed of up to 25 km / h. The transition of the gun from the combat position to the stowed position with a separate carriage took from 45 minutes to 2 hours, depending on the time of year and the type of soil. The gun was towed by the Voroshilovets tracked tractors, and the barrel carts by the Comintern tracked tractors.
Mortar Br-5 had caps loading. For firing from a mortar, concrete-piercing and high-explosive shells were used. The firing tables provided for the use of 11 variable charges weighing from 9, 88 to 3, 45 kg of gunpowder. The charge scale is individual for each of the shells used. For the G-675 projectile, a full variable charge Z-675B (5 charges) and a reduced variable charge Z-675BU (6 charges) were used, for the F-674K projectile - a full variable charge Z-675 (2 charges) and a reduced variable charge Z-675U (3 charges), for the F-674 projectile - a full variable charge Z-675A (3 charges), for the F-674F projectile - a full variable charge Z-675F (4 charges).
The rate of fire of the mortar was 1 shot in 4 minutes.
The Soviet artillery inherited from the Russian Imperial Army two samples of especially powerful artillery systems - the 280-mm Schneider mortar mod. 1914/15 and a 305-mm howitzer mod. 1915 By the mid-1930s, these tools became obsolete both morally and physically, in addition, their number was assessed as insufficient. It became necessary to create and launch into mass production of new samples of especially powerful guns, including 280-mm mortars. The caliber of the new artillery system was determined by the desire to use the available ammunition stocks. Since the 203-mm B-4 howitzer was put into service in 1931, and the development of a 152-mm long-range cannon project was underway, it was decided to create a triplex - three different artillery systems using the same gun carriage, which greatly simplified the production and operation of the guns. As in the case of the 152-mm long-range cannon, the rival design bureaus of the Bolshevik and Barricades plants were engaged in the creation of the 280-mm mortar.
The mortar project of the Bolshevik plant received the index B-33, the project was managed by engineer Krupchatnikov. The barrel of the mortar was made in 1935, the mortar was sent for factory tests on February 1, 1936. The design features of the gun were a fastened barrel from a pipe, a casing and a breech, as well as a piston bolt from Schneider's mortar. The barrel was mounted on the carriage of the B-4 howitzer without a balancing mechanism, since it was balanced by adding a load to the breech. The mortar was sent to field tests on April 17, 1936, on the whole they were completed successfully and, based on their results, it was recommended to send the mortar for military trials after eliminating the identified deficiencies.
At the Barricades plant, the project of the 280-mm mortar, which received the Br-5 index, was led by I. I. Ivanov. Factory tests of a prototype mortar were carried out in December 1936. In April 1937, the prototype modified according to the results of factory tests was delivered to the Research Artillery Range (NIAP) for field tests. The landfill specialists fired 104 shots from the mortar and in November of the same year delivered their verdict: "The Br-5 did not pass the field tests and cannot be admitted to military tests without correcting defects and repeated field tests."
Nevertheless, it was the Br-5 that was put into mass production under the official name “280-mm mortar mod. 1939 , and the first order for the manufacture of mortars was issued even before the end of field tests, in May 1937. The reasons for choosing the Br-5 instead of the B-33 are unknown; on tests, the latter showed better results, in particular, greater accuracy and a higher rate of fire, and was also less massive than the first.
The first order for 8 Br-5 mortars was issued to the Barricades plant in May 1937. Later, due to the incompleteness of the system, the number of guns ordered for 1937 was reduced to two, but they could not be manufactured either in that year or in the following year. These two experimental mortars were delivered to the test site in June 1939 and differed from each other in the way they were loaded. According to the test results, a loading method was chosen, similar to that used in the B-4 howitzer. In addition to these two prototypes, 20 more mortars were manufactured in 1939, and in 1940 - the last 25 guns, on which their mass production was discontinued.
The unsuccessful design of the gun carriage of the triplex guns became the basis for initiating work on the development of a new wheeled carriage, devoid of the shortcomings of the original tracked structure. In 1938, the Main Artillery Directorate approved the tactical and technical requirements for a new wheeled carriage for a high-power duplex (152-mm gun Br-2 and 203-mm howitzer B-4), in 1940 it was proposed to develop this carriage for the Br-5. The executor of the task was the design bureau of plant No. 172 (Perm plant) under the leadership of F. F. Petrov. The carriage received the M-50 index, but work on it proceeded extremely slowly due to the heavy workload of the design bureau with work on other systems. As a result, by the beginning of the war, everything was limited to the development of the project, after which all work was stopped.
In 1955, the Br-5 underwent a major modernization, a new wheeled carriage was developed for these mortars (the chief designer of the project was G. I. Sergeev). The transport of the gun became inseparable, and its speed increased to 35 km / h. Mortars Br-5M were in service until at least the 1970s.
Mortars Br-5 took part in the Soviet-Finnish war, four of these mortars since November 1939 were part of the 40th separate high-power artillery battalion. Mortars took part in breaking through the Mannerheim Line, destroying Finnish bunkers. In total, during this war, Br-5 mortars fired 414 shells.
By the beginning of the Great Patriotic War, 47 mortars were in service with eight separate artillery divisions of the RGK's special power. Br-5s were used in battles on the Karelian Isthmus in 1944, during the assault on Neustadt, Konigsberg and during the Berlin operation.
