B-4 M1931 203-mm howitzerThe M1931 (B-4) is a rather old weapon developed in 1931 and adopted for service in 1934. The modified version (B-4M) with four-wheeled carriage appeared only after World War II. It may be found in the heavy artillery brigade at front level. The B-4M was replaced by the 203-mm self-propelled gun Ml975, which is mounted on a tracked chassis.
The 203-mm howitzer M1931 (B-4) has a relatively short tube, only 25 calibers long. It has a hydraulic recoil buffer, a hydropneumatic recuperator, and a screw-type breechblock, and fires bag-type, variable-charge, separate-loading ammunition. Early models were mounted on a full-track (but not self-propelled) carriage in firing position and for short moves. For longer moves, the tube was removed and transported on a separate four-wheeled tube transporter. On later models (B-4M) the tracked carriage was replaced by a large four-wheeled carriage to permit long moves without removing the tube. In firing position, the wheels of the B-4M are raised, and the weapon rests on a firing platform. Both models use the same box trail and are towed by the AT-T tracked artillery tractor.
The M1931 fires a 98.8-kg HE round to a maximum range of 18,025 meters. It also has been adapted to fire a nuclear round. The M1931 has a very limited traverse of 8 degrees and a slow rate of fire of 0.5 rd/min (some reports indicate 1 rd/min).
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