This was the second production version of the M5, which can be distinguished by the extended M3A3 turret model. The turret itself helps to distinguish between the early and later models, as on the early models, there were still pistol ports in the side walls. The extra bustle provided room for the more powerful SCR 508 radio and antenna mounted at the extreme rear. To avoid interference with it, the cal.30 (7.62 mm) pintle mount had to be shifted from the back plate to the right hand side turret wall. Because of this, it could only be fired by one of the crew -often the commander- from inside the turret, a considerable advantage for protection. But the cal.30 (7.62 mm) had been woefully criticized in action as being totally inefficient against the fast-flying aircraft of 1942-43.