User blog comment:PFC Arkalis/Battlefield 3 Unlocks and Rewards; New Battleblog/@comment-1990578-20110805210624/@comment-1439572-20110808134232

In 2142 UB GL and UB Shotgun use the same ammo pool if you slap both of them into the gun.

And 2142 weapons are futuristic (duh), they probably have empty sockets for modular attachments like launchers and stuff.