A tank cannot keep extending its gun barrel without making the vehicle harder to move. The gun has to remain practical for passing through restricted spaces and for transporting the tank. Increasing caliber is therefore presented as another route to a larger shell when barrel length is constrained. Ships face a different set of limits, so tank and naval gun sizes cannot be compared on caliber alone.
Notable Point · 3:52:05-3:52:47
Why tank mobility limits gun-barrel length
Barrel length has practical movement and transport limits, which helps explain why tank-gun development can favor a larger caliber.