100 mm/47 O.T.O. Mod. 1928 (100 mm)

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Triple-turret battery of the 100 mm/47 O.T.O. Mod. 1928 on RN Eugenio di Savoia


The 100 mm/47 O.T.O. Mod. 1928 is an Italian naval gun. It serves as a secondary multi-purpose gun in open twin-gun turrets on a number of Italian cruisers. Being a relatively old design, it struggles with rate of fire and the damage inflicted by an individual shell. But overall it offers an important component of the anti-air defence for the cruisers, being able to engage bombers even a few kilometres up when controlled by the AI gunners.

Vehicles equipped with this weapon

General info

Available ammunition

Penetration statistics
Ammunition Type of
Penetration @ 0° Angle of Attack (mm)
100 m 1,000 m 2,000 m 3,000 m 4,000 m 5,000 m
HE Dirompente HE 17 17 17 17 17 17
HE-TF Contro-aerea HE-TF* 17 17 17 17 17 17
APHE Perforante APHE 150 129 109 93 78 67
Shell details
Ammunition Type of
mass (kg)
Fuse delay
Fuse sensitivity
Explosive mass
(TNT equivalent) (g)
0% 50% 100%
HE Dirompente HE 850 13.2 0 0.1 1,300 79° 80° 81°
HE-TF Contro-aerea HE-TF* 850 13.2 0 0.1 1,300 79° 80° 81°
APHE Perforante APHE 850 13.8 0.01 6 820 47° 60° 65°

Comparison with analogues

Comparing to the foreign equivalents of a similar calibre the 100 mm/47 O.T.O. Mod. 1928 is rather underwhelming weapon, showing its age when matched against more modern counterparts. For starters, it lacks HE-VT shells that its British and Soviet equivalents have access to, and thus it offers a much lower anti-air potential with its plain HE-TF shell. The filler in the high-explosive shells is also one of the lowest, thus being limited in the amount of damage done. This is made worse by a very low rate of fire (owning it to a fully manual operation of the gun by the crew), low targetting speed and a low muzzle velocity. In fact, the gun suffers from having a low reload rate even compared to the variant of the same gun found on the Soviet ships, designated Minizini.

There are two upsides however: unusually for the calibre (and owning it to the dated design), the gun comes with a dedicated APHE shell that can penetrate the hulls of most destroyers and even a number of cruisers, though a low number of guns and the inaccuracy of the AI gunners against bluewater ships make it an unlikely mean of sinking enemy warships. The other saving grace of these guns is their long range, similar to the foreign equivalents, which allows them to harass enemy bombers long before they get ready to drop their bombs, thus discouraging enemy from attempting engagement.


Cannon Ammo Calibre
Muzzle Velocity
Sustained rate of fire
Targeting speed
TNT Equivalent
@ 0° Angle of Attack (mm)
Horizontal Vertical 1,000 m 5,000 m
Kingdom Italy flag.png 100 mm/47 O.T.O. Mod. 1928 HE 100 850 9.6 11 6 1.3 17 17
USSR flag.png Minizini (100 mm) HE 100 800 12 11 6 1.24 45 26
USSR flag.png 100 mm/70 SM-5-1 HE 100 1,000 15 14 14 1.94 24 24
USSR flag.png 100 mm/56 B-34 HE 100 900 15 21 17 1.95 24 24
Britain flag.png 4 inch/45 Mark XVI HE 102 811 10 20 6 8.5 20 20
Germany flag.png 10.5 cm SK C/32 HE 105 875 15 6.8 6.8 1.55 20 20
Japan flag.png 100/65 mm Type 98 mod A HE 100 950 15 12 16 0.95 13 13

AP and SAP

Cannon Ammo Calibre
Muzzle Velocity
Sustained rate of fire
Targeting speed
TNT Equivalent
@ 0° Angle of Attack (mm)
@ 60° Angle of Attack (mm)
Horizontal Vertical 1,000 m 5,000 m 1,000 m 5,000 m
Kingdom Italy flag.png 100 mm/47 O.T.O. Mod. 1928 APHE 100 850 9.6 11 6 0.82 129 67 52 29
Britain flag.png 4 inch/45 Mark XVI SAP 102 811 10 20 6 0.6 102 64 43 27

Usage in battles

These guns are used exclusively as secondaries and unlike a number of other secondary guns on cruisers - they are best left for the AI to control at all times, as the guns simply lack both punching power and/or rate of fire to be worth being manually-controlled, maybe with exception of the Zara-class where three-turret broadside is just-about enough to save the day in specific circumstances. These guns should be primarily thought of as a psychological warfare against enemy airplanes: they offer just enough fire to look discouraging, while also being able to score a random hit every now and then. They are by no means reliable, but still better than having no long-range protection (an issue Japanese warships struggle with throughout the research tree).

Pros and cons


  • Good APHE shell for the calibre
  • Long engagement range


  • Poor damage potential (small explosive fillers in HE shells, low rate of fire, poor muzzle velocity)
  • Lack of HE-VT shells
  • Low targeting speed


The Austro-Hungarian Empire began to lay down plans for a much expanded naval force in the early 1900s. No longer content with a coastal defense force, they wanted to have control over the Adriatic Sea. The change was influenced by the politics of Marinekommandant (Chief of the Navy) Rudolf Montecuccoli and crown prince Archduke Franz Ferdinand who viewed Italy as a threat, along with the new railway linking their ports at Trieste (present-day Italy) and the Dalmatian coastline (present-day Croatia) to the rest of the Empire. The new fleet expansion program led to orders for a new cannon to arm their destroyers and scout cruisers leading to the Škoda K 10 first developed in 1907 and adopted in 1910. After World War I ended, the Austro-Hungarian Empire was dismantled by the Allied Powers. This dismantling included the navy with Italy getting the K 10 guns on the Brindisi and Venezia which were ships ceded from the Austro-Hungarian Navy as war reparations.

The Italians were so enamoured with the design, they began to produce the design locally through OTO which resulted in a variety of different variants of the design. The O.T.O. Mod.1928 was a dual-mount anti-aircraft variant with electrically powered adjustable trunnions, rope rammers and mechanized spring, and a loose liner. Despite being intended for anti-aircraft use, the gun was too slow for this role, particularly if a ship was rolling and it was instead more suited for barrage fire. The RN Balzano, Condottieri-class, RN San Giorgio, and Zara-class cruisers all used these guns. They were also used on the Conte di Cavour-class dreadnoughts. The Soviet Navy also used this gun as the Minizini named for the developer of the duel mount Italian Commandante Minizini.


Excellent additions to the article would be video guides, screenshots from the game, and photos.

See also

External links

Italy naval cannons
20 mm  20 mm/65 Breda · 20 mm/70 Oerlikon 3S · 20 mm/70 Scotti-Isotta Fraschini mod.1939
37 mm  37 mm/54 Breda Mod.32 · 37 mm/54 Breda Mod.38 · 37 mm/54 Breda Mod.39
40 mm  40 mm/39 Vickers-Terni mod.1915/1917 · 40 mm/39 Vickers-Terni mod.1915/1917, Modif.1930 · 40 mm/70 Breda-Bofors type 107
65 mm  65 mm/64 Ansaldo-Terni Mod.1939
76 mm  76 mm/40 Armstrong mod.1897/1910 · 76 mm/40 Armstrong mod.1897/1912 · 76 mm/40 Ansaldo mod.1917 · 76 mm/45 Schneider mod.1911 · 76 mm/50 Vickers mod.1909 · 76 mm/62 OTO-Melara Compact · 76-mm/62 SMP 3
90 mm  90 mm/50 Ansaldo model 1939
100 mm  100 mm/47 O.T.O. Mod. 1928 · 100 mm/47 O.T.O. Mod. 1937
120 mm  120 mm/45 Canet-Schneider-Armstrong mod.1918-19 · 120 mm/50 Armstrong model 1909 · 120 mm/45 O.T.O. Mod. 1926 · 120 mm/50 Ansaldo mod.1926 · 120 mm/50 O.T.O. Mod.1936
135 mm  135 mm/45 O.T.O. Mod. 1937
152 mm  152 mm/45 Schneider mod.1911 · 152/53 mm Ansaldo mod.1926 · 152/53 mm O.T.O. Mod.1929
203 mm  203 mm/50 Ansaldo mod.1924 · 203 mm/53 Ansaldo mod.1927
305 mm  305 mm/46 Armstrong model 1909 · 305 mm/46 Vickers model 1909
320 mm  320 mm/44 OTO model 1934 · 320 mm/44 Ansaldo model 1936
20 mm  2 cm/65 Flakvierling 38 (Germany) · 20 mm/70 Oerlikon Mk.II (USA)
40 mm  Bofors L/60 Mark 1 (USA) · Bofors L/60 Mark 3 (USA)
76 mm  76 mm/50 Mk.33 (USA)
127 mm  127 mm/38 Mk.12 (USA)