And that is why sub machine guns while an issue item were not kept. The idea was self defense after a bail out or in lager.
Inside a tank there was no room, ergo the pistols.
Most of the time they would have been camped with infantry, carbine good enough and a lot easier to shoot well.
My grand father was a Sherman tanker from 41 to 45. He had 5 tanks knocked out from under him. The first in North Africa hit a land mine. He was sitting in the commanders hatch and was blown clear. No one else in the crew made it. The others were , track shot off twice, main gun hit and cut in half. Turrent strike did not penetrate but turrent was stuck. He only talked about initially carrying a revolver and later a 1911. I never heard him say much about any long gun. He had Some experience unassing Shermans and bugging out. On the main gun and stuck turrent they drove out. He was 28 when he joined in early 41. All of his crew members called him Gramps.