Corki R Cooldown Not Affected by CDR. Does Not Match Tooltip.
tldr; Corki's rocket cooldown is fixed at 2.0sec even though the cooldown tooltip says 0.97sec.
Corki's R rockets cooldown is not affected by CDR. By default you can fire a rocket every 2.0sec. With 40% CDR + 19% ult CDR from Ultimate hunter + cloud dragon the CDR is reduced to** 0.97s according to Corki's R rocket tooltip**. (2.0sec * 0.6 * 0.81 = 0.97sec) However, the actual cooldown is still 2.0sec even though the tooltip says 1.09sec.
The rocket recharge rate is correctly affected by CDR, it's just the cast interval that is bugged and does not match the toolip.