How fast could turrets rotate?
The vaunted Panther tank had, in its first iteration (Panther Ausführung D), one of the slowest-turning turrets in the war, taking a full minute to traverse 360º. The gearing on the turret was changed in the Ausf. A, the next version, and all subsequent Panthers, giving the tank a competitive 15-second full-circle. But that didn’t last; a November, 1943 decision to govern the engine to a lower max RPM reduced slew rate to 18 seconds on Panthers from that point forward — if the crews didn’t learn about and adjust the governors. This was done to try to increase engine reliability: more Panthers were being lost to breakdowns than to Allied gunfire.
What’s interesting is that even though the early Panther turret was quite slow, it was still fast enough to track all but the fastest-moving tanks. All greater speed than a circle-a-minute buys, then, is ability to change targets, or get on a sighted target, faster.
The American system spun a Sherman turret 360º in fifteen seconds, too. The system in the M36 tank destroyer had the same performance, also. (Not surprising as the automotive gear in the tank destroyers was lifted from the Shermans).
The undisputed slewing champ of WWII tanks was the Russian T-34, which could bring its turret all the way around in 12 seconds.
We couldn’t find any credible information on the slew or traverse rate of Japanese tanks.
The final lesson in all of this brings us back to convergent evolution: despite the different approaches taken by the major tank producers of the era, their performance was roughly similar (excluding the lagging Japanese, who deemphasized tank development and production because of their limited production capacity, and overwhelming naval requirements).
