impotent against the heavily armoured British Matilda II, at a weight of 13 tons it carried armour comparable to most of its opponents of 1940–41 and its 47 mm long-barrelled gun was effective against many other British tanks of 1940–41, which were similarly armoured to the M13 but carried 2pdr (40 mm) guns with shorter range and inferior ballistic performance. At that time, most German tanks were armed with 20 mm, 37 mm guns or 50 mm and 75 mm low velocity guns. Only after 1942 did the Germans start the widespread adoption of weapons of 50 mm and 75 mm calibre long barreled guns with high enough velocity for adequate anti-tank use, which gave the M13/40s gun an advantage over comparable German tanks in the early war. The adoption of the 47 mm long gun was probably the best feature of the M13. Due to its relatively large calibre, the main gun's HE round was also very useful against towed guns and infantry, and eliminated or at least mitigated, for the first years of war, the need for a dedicated support vehicle such as the Wehrmacht had in the early Panzer IV and Stug III. The diesel engine was an advantage, and the simplicity of production suited the state of Italian industry. However, the tank also had many grave shortcomings which severely hampered its effectiveness on the battlefield: the engine provided good range, but not great power and reliability. The M13's engine was the same as the M11's, but the newer tank was heavier, which resulted in lower speed and more strain on the powerplant. The suspension and tracks were reliable, but resulted in relatively low speeds, not much better than infantry tanks such as the Matilda. Armament was sufficient for 1940–41 but did not keep up with the increased armour and firepower on Allied or German tanks. The method of construction, using rivets, was outdated. Most tanks of the era were switching to the use of welding for construction, since rivets can shear off when hit, becoming additional projectiles inside the tank. The two-man turret was less efficient in combat than the three-man turrets used in many other tanks of the era. Radios were not fitted to many tanks. Italian historians Filippo Cappellano and Pier Paolo Battistelli have pointed out that the disappointing performance of the tank early in the war, where its armament was by no means