I hate to be a pest about this, but open or closed bolt design has nothing to do with the cyclic rate, and very few firearms can fire from both the open and closed bolt. It's either one method or the other.
As a side note, open bolt firearms designs are prohibited and controlled by ATF Ruling 82-2.
I always thought the open/closed bolt thing was that in a closed bolt weapon after extended automatic firing the next unfired round sat in a very hot chamber and could go off by itself, whereas an open bolt would not have that defect. Correct?