Why the six-inch cruiser gun survives without treaty limits

Would the six-inch and eight-inch cruiser-gun divide survive without Washington treaty limits?

Six inches would probably remain important because it is near the upper limit for fast manual ammunition handling, although some navies might explore an intermediate gun around 7.5 inches.

Treaties formalized the light- and heavy-cruiser categories, but they did not create every technical boundary beneath them. Six-inch ammunition can still be handled rapidly by crews, preserving a high rate of fire that heavier weapons struggle to match. Without the treaty, the upper category might grow toward 12-inch armored ships while six-inch cruisers remain useful for a different firing cycle.