The Improved Carbine is intended as a no holds barred look at individual small arms in the carbine class. Despite rumors that the Improved Carbine and Squad Individual Marksman variant would share the same requirements document, possibly also with the Personal Defense Weapon, this is not the case. They needed to be broken down into separate requirements although it is possible that the Individual Carbine and Squad Individual Marksman weapons may end up relying on a common weapon. The PDW is a bit more problematic due to the Army’s desired characteristics for the weapon. The Army wants to purchase about 500,000 of the new carbines and has stipulated that they will own the Technical Data Package so that they can award production contracts for the type selected to more than one manufacturer.
http://soldiersystems.net/2010/04/12...my-small-arms/