Russian
100 mm/51 (3.9") B-24 Pattern 1936
100 mm/56 (3.9") B-24BM Pattern 1939
Updated 11 September 2006
In 1932 the "Bolshevik" factory was tasked to create a new 100 mm (3.9") gun for use in submarines and small combatants.  The first gun was made in 1935 and trials lasted until 1936, when it was accepted in to service.  In 1937 the gun was modified and was redesignated B-24-IIc.

In 1938 the design was lengthened to 56 calibers and accepted into service in 1939.  This new design used a gun shield and was for small combatants.

By 1941 there were 76 guns of both types in service.  During the war only five B-24 guns were made but in 1946-50 a further 63 were made for use on submarines.

The B-24 gun was made from A tube, fastened with a casing which was assembled while the gun was hot.  The B-24BM gun was made from loose-liner, casing and breech.  The breech mechanism was semi-automatic pneumatic horizontal sliding breech-block in the guns made prior to 1942 and a spring-driven semi-automatic breech in all later versions.  All of the mechanisms in both guns were identical except for the gun sight and the shield.
WNRussian_39-51_m1936_Sub_pic.jpg

100 mm/51 (3.9") Pattern 1936
WNRussian_39-51_m1931_side_pic.jpg

100 mm/51 (3.9") Pattern 1936
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Gun Characteristics
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Designation 100 mm/51 (3.9") B-24 Pattern 1936
100 mm/56 (3.9") B-24BM Pattern 1939
Ship Class Used On B-24 PL
   L class (series II, XI, XIII, XIII-38), S class (series IX, IXbis, XVI), K class (series XIV)
   D class (series I) (rearmed), MZ class (Project 99) (cancelled) submarines

B-24BM
   Uragan class patrol ships , Purga class patrol ships, Verp' class, Paravan class, Fugas class
   Vladimir Polukhin class minesweepers, various minelayers, various armed icebreakers
   Miscellaneous transports, coastal defense guns
Date Of Design B-24:  1935
B-24BM:  1938
Date In Service B-24:  1936
B-24BM:  1939
Gun Weight B-24:  2.387 tons (2.425 mt)
B-24BM:  2.671 tons (2.713 mt)
Gun Length oa B-24:  200.79 in (5.100 m)
B-24BM:  228.15 in (5.795 m)
Bore Length B-24:  190.95 in (5.100 m)
B-24BM:  210.63 in (5.350 m)
Rifling Length B-24:  162.21 in (4.120 m)
B-24BM:  182.09 in (4.625 m)
Grooves 40
Lands N/A
Twist N/A
Chamber Volume 155.6 in3 (2,550 cm3)
Rate Of Fire 12 rounds per minute
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Ammunition
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Type Fixed
Weight of Complete Round about 61.7 lbs. (28 kg)
Projectile Types and Weights AA grenade - 34.39 lbs. (15.6 kg)
AA (ZS-56) - 34.39 lbs. (15.6 kg)
AA (ZS-56P) - 35.05 lbs. (15.9 kg)
HE mod 1928 (F-56) - 34.83 lbs. (15.8 kg)
Diving - 33.07 lbs. (15.0 kg)
Star Shell (SB-56) - 35.27 lbs. (16.0 kg)
ECM (anti radar) (PB-56) - N/A
Bursting Charge AA grenade - 2.67 lbs. (1.21 kg)
AA (ZS-56) - 2.71 lbs. (1.23 kg)
AA (ZS-56P) - 1.74 lbs. (0.79 kg)
HE mod 1928 (F-56) - 2.76 lbs. (1.25 kg)
Diving - 6.28 lbs. (2.85 kg)
Star Shell (SB-56) - 0.03 lbs. (0.015 kg)
ECM (anti radar) (PB-56) - reflective material DOS-15
Projectile Length AA grenade - 5.3 calibers
AA (ZS-56) - 5.13 calibers
AA (ZS-56P) - 5.0 calibers
HE mod 1928 - 5.2 calibers
Diving - 5.04 calibers
Star Shell (SB-56) - 5.2 calibers
Propellant Charge 13.2 lbs. (6 kg)
Muzzle Velocity B-24
   AA grenade - 2,861 fps (872 mps)
   HE mod 1928 - 2,638 fps (804 mps)
   Diving - 820 fps (250 mps)

B-24BM
   AA grenade - 2,953 fps (900 mps)
   HE mod 1928 - 2,936 fps (895 mps)
   Diving - 820 fps (250 mps)
   Star Shell (SB-56) - 2,119 fps (646 mps)
Working Pressure 3100 kg/cm2
Approximate Barrel Life 800 rounds
Ammunition stowage per gun K-class, S-class,  submarines - 200 rounds
L-class (series II, XI) submarines - 122 rounds
L-class (series XIII, XIII-38) submarines - 150 rounds
Uragan class - 150 rounds
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Range
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Elevation With 34.4 lbs. (15.6 kg) HE Shell
Maximum Range (B-24BM) 24,323 yards (22,241 m) 
Maximum Range (B-24) 24,402 yards (22,314 m) 
Elevation With 34.4 lbs. (15.6 kg) AA Shell
Maximum Timer Range (B-24BM) 10,821 yards (9,895 m)
Maximum Timer Range (B-24) 10,551 yards (9,648 m)
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Mount / Turret Data
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Designation Single Mounts:  B-24, B-24-IIc, B-24BM, B-24PL
Weight B-24BM:  7.284 tons (7.4 mt)
B-24-IIc:  5.217 tons (5.34 mt)
B-24PL: 5.414 tons (5.5 mt)
Elevation -5 / +45 degrees
Rate of Elevation 5 degrees
Train 360 degrees
Rate of Train 5 degrees
Gun Recoil @ 0 degrees:  24.43 in (595 mm)
@ 85 degrees:  26.77 in (680 mm)
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Data from
"Sovetskie Boevye Korabli 1941-45:  IV Vooruzhnie" (Soviet Warships 1941-45:  Volume IV Armament) by A.V. Platonov
"Entsiklopedia Otechestvennoi Artillerii" (Encyclopedia of Fatherland (Russian) Artillery) by A.V. Shirokorad
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"Flot vo Slavu Rossii" (Fleet in Honor of Russia) CD
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Special help from Vladimir Yakubov