A former Italian tank regiment commander said :
"The M13/40 had good maneuverability, an accurate 47mm gun, effective optical equipment (gunsight and periscopes) for external vision, and good crew habitability. The tank's armor was sufficiently thick, but lacked tensile strength. The modestly fuel efficient diesel engine did not easily catch fire when hit by gunfire; however, the engine’s lack of power made the M 13-40 an underpowered vehicle. The vehicle’s low speed over uneven ground and slopes made the tank vulnerable."
The British however :
"We captured several M 13-40s during the 1940 offensive and observed that this vehicle's main failures were its poor bullet splash protection and its light armor. These drawbacks were made worse by poor training for Italian tank crews during 1940, when they received only 25 days and two driving hours before going into combat. The Italian tanks were also made ineffective by inept leadership in the field."
Source: Nicola Pignato, "Italian Medium Tanks in action"
The Breda 38, which resembled the Bren LMG, was developed in 1938 from the Breda 37. When used in the anti-aircraft role, a ring and post sight was fitted to the gun's left side. The Breda could only be fired from the open hatch and there were no provisions for ground use (ie buttstocks, bipods or iron sights).
"Within a year after it's introduction in 1940,
the M13 was undergunned and underarmored.
The running gear required massive amounts of lubrication,
the crew compartment was cramped, while
the power plant and the filters were insufficient for hard desert use.
Crew communication in battle was awkward and frustrating. Finally,
the armor plates were brittle and prone to shattering and even complete disintegration."