Wikipedia in Italian Army equipment in WW1.
Field Artillery

Italian artillery was usually designated using the calibre and length of the barrel in number of calibre lengths, so "90/53" would mean a weapon with a 90 mm diameter barrel where the length of the barrel was approximately 53 calibre lengths (i.e. 53x90 mm, that is 4.77 m).
ModelCaliberMax. rangeFromProducedWeight, kgfire rate, RPMComment
Cannone da 47/32 M35 47mm 7000 1935 ? 315 5 dual-role anti-tank/infantry gun, adopted for many vehicles, licensed version of Böhler gun
Cannone da 65/17 modello 7 65mm 6800 1907 ? 650 5 mountain gun
Cannone da 65/17 modello 13 65mm 6800 1913 ? 650 5 mountain gun
Skoda 75 mm Model 15(Obice da 75/13) 75mm 8250 1918 ? 613 7 Austrian-built
Cannone da 75/27 modello 06 75mm 10000 1906 ? 1080 5 licensed version of Krupp 1906M gun
Cannone da 75/27 modello 11 75mm 10240 1912 ? 1076 5 French-designed
Cannone da 75/27 modello 12 75mm 10000 1912 ? 900 5 modification of Cannone da 75/27 modello 06
Obice da 75/18 modello 34 75mm 9564 1934 ? 1832 5 mountain gun
Obice da 75/18 modello 35 75mm 9564 1935 ? 1832 5 howitzer and export variant of Obice da 75/18 modello 34
Cannone da 75/34 modello 37 75mm 12500 1937 1 1250 5 prototype of 75/32 field gun, unmodified 75/34 went on as tank gun
Cannone da 75/32 modello 37 75mm 12500 1937 ? 1250 5 dual-role anti-tank/field gun
Cannone da 77/28 modello 5/8 76.5mm 6100 1907 ? 1065 9 built in Austria-Hungary, bronze barrel
Obice da 100/17 modello 14 100mm 8180 1914 ? 1417 6 Austrian-built, in NATO service until 1984
Obice da 100/17 modello 16 100mm 8180 1916 ? 1235 6 weight reduction of Obice da 100/17 modello 14 for use as mountain gun
Cannone da 105/28 modello 12 105mm 8000 (12000) 1917 854 2650 5 France-built, kept in reserve until 1939
Obice da 105/14 modello 17 105mm 6000 (8100) 1917 120 1400 5 used in self-propelled gun
Cannone da 120/21 120mm 7700 1880 5 4050 5 fortress Krupp gun, used by Italian border guards
Cannone da 149/23 149.1mm 9300 1882 ? 6050 1 fortress howitzer, most likely did not see combat in WWII
Obice da 149/12 modello 14 149.1mm 6500 1915 ? 2700 1.5 Austrian-built Skoda howitzer
Obice da 149/13 modello 14 149.1mm 8800 1915 490 2765 1.5 Obice da 149/12 modello 14 modified for new ammunition
Cannone da 149/35 A 149.1mm 16500 1900 895 8220 1 No recoil absorber, zero traverse
Obice da 149/19 modello 37 149.1mm 14250 1939 230 5780 3 Italian replacement for all older howitzers
15 cm/50 K10 Skoda 149.1mm 15000 1912 12 ? 6 removed from Austrian battleship Tegetthoff and used in coastal defense
Cannone da 152/45 152.4mm 19400 1910 53 16672 1 Naval gun used in counter-battery fire and siege
Cannone da. 152/37 152.4mm 16000 1916 44 11900 1 built in Austria-Hungary
190/39 Skoda 190mm 20000 1904 29 12700 3 built in Austria-Hungary as naval gun, reused by Italians in coastal defense
7.5"/45 model 1908 191mm 22000 1908 24 13770 2.6 naval gun reused in coastal defense
203/45 modello 1897 203.2mm 18000 1897 40 11900 2.4 built for Giuseppe Garibaldi-class cruisers, used in WWII as siege gun and coastal defense
203/50 modello 24 203.2mm 30620 1924 26 11900 2.4 built for Trento-class cruisers, 1 turret used in coastal defence
Obice da 210/22 modello 35 210mm 15400 1935 20 24000 1 Production continued by Germans after surrender of Italy
Mortaio da 210/8 D.S. 210mm 8450 1900 ? 10930 0.4 In Italian fortresses only
Mortario da 210/8 PIAT 210mm 8450 1900 ? 10930 0.4 Towed version of Mortaio da 210/8 D.S.
Mortario da 210/8 FROM 210mm 8450 1900 ? 10930 0.4 Improved mobility version of Mortario da 210/8 PIAT
Skoda 305 mm Model 1911 305mm 9600 1911 79 20839 0.18 Austro-Hungarian siege howitzer, received by Italy
305/50 mod. 1912 305mm 19000 1909 6 199900 1 naval gun used as coastal artillery
305/45 K10 Skoda 305mm 20000 1911 65 620000 3 triple-mount Austrian naval gun used as coastal artillery
Cannone navale da 381/40 (coastal) 381mm 27300 1912 10 95000 1.75 naval gun used as coastal artillery
Cannone navale da 381/40 (railroad) 381mm 30000 1912 7 212000 1.75 naval gun used as railroad gun
See also:

• Mortar da. 260/9 1916M (used in Spanish civil war)
• 203 mm /53 Italian naval gun - main gun on Italian cruisers