Something strange happend just now.

Dakiras:   Just wanted to add to this... a lot of the tanks share researched parts from its predecessors, so it's always a good idea to make a thorough review of the tanks you intend to progress through, as it's often easier to research a gun on a lower tier tank that will also be available in the next tier. I learned this the hard way. :)   If you look at the characteristics of the modules, it'll tell you which tanks use it.