I received more information about the tank commander's position..... We have worked on a solution to the issue of the tank commander being exposed when he fires the .50 cal.  It is part of Tank Urban Survivability Kit (TUSK).  
 
Description: A remotely fired weapon station for the Commander of the M1A2 SEP Abrams Tank.  
Consists of mount for existing .50 cal MG, day and night sights, for 360 degree operations. 
*Cost: $150,000 per vehicle
*Previous Fielding: Fielded to support combat operations (Various platforms; RWS is on STRYKER