Re: Military FAQ
Welcome aboard FSMonster, yes, this is the good place to ask anykind of question about any army. But for you two question, that's not my domain, you should ask Gollevainen (a artilleryman) or Utelore (former tanker). Well I can only answer part to your question.
Yes, the thermal sleeve is made to prevent bending, because there's a high temperature at each shot, and when it goes to hot, the metal will bend, it's like a machine gun barrel, after long burst or long time continous firing, you need to change the barrel because it heated too much and the accuracy is affected, but it's much harder to change a tank gun than a machine gun barrel, so that's why there's a thermal sleeve to cool the gun.
And yes, the middle part is a fume extractor.