Unless the halftrack got some kind of speed buff added to the flame upgrade that I'm not aware of, it isn't capable of moving out of an AT gun's arc of fire in time to avoid the second hit even if it starts moving within half a second after being hit due to its horrific acceleration, nightmarish turn speed (which comes into play unless you miraculously give a move order directly in front or behind, which barely ever happens) and low movement speed overall.
Maybe don’t drive your flametrack halfway into an at gun’s arc and just stop then.
@armadillo: the machine gun arc thing is a bug with garrisons I think. The visual arc you see if you click on an mg in a garrison originates from the center of the building and not the actual weapon. The real arc is visible if you select the squad in the garrison rather than the building.
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Heartless Jäger 
