 The defence was supported by a strong artillery component that included 41 Breda Model 35 20 mm antiaircraft guns ; 85 47 mm antitank guns ; 26 Solothurn S @-@ 18 / 1000 anti @-@ tank rifles ; 41 Cannone da 65 / 17 modello 13 65 mm infantry support guns ; 147 Cannone da 75 / 32 modello 37 75 mm and 77 mm field guns ; 76 Skoda 100 mm Model 1916 and Canon de 105 mle 1913 Schneider 105 mm guns ; and 27 120 mm and Obice da 149 / 12 modello 14 149 mm medium howitzers . The large number of different gun models , many of them quite old , created difficulties with the supply of spare parts . The older guns often had worn barrels , which caused problems with accuracy . Ammunition stocks were similarly old and perhaps as many as two @-@ thirds of the fuses were out of date , resulting in excessive numbers of dud rounds . There were also multiple models of machine guns , with seven different types of ammunition in use . The Breda 30 , the principal light machine gun , had a low rate of fire and a reputation for jamming . The Fiat @-@ Revelli Modello 1914 was a bulky and complicated weapon that was also prone to stoppages . Some of these had been rebuilt as Fiat @-@ Revelli Modello 1935s which , while an improvement , were still unreliable . The principal medium machine gun , the Breda M37 , had its shortcomings , the main one being that it used 20 @-@ round strips of cartridges , which gave it a reduced rate of fire . Shortages of raw materials , coupled with the increased technological sophistication of modern weapons , led to production problems that frustrated efforts to supply the entire Italian Army with the best available equipment . The result was that the firepower of the Italian defenders was neither as great nor as effective as it should have been . 
