Pfc. Phillip Ruiz, from 2nd Platoon, Company B, 2nd Battalion, 1st Infantry Regiment, provides security for Soldiers and Marines during a presence patrol in Rawah, Iraq.
Pic from Army.mil.
The short-barreled/sliding-stock version of the SAW (Squad Automatic Weapon) is 10 inches shorter than the standard model and is particularly handy for airborne troopers and urban operations. Not sure what the performance loss is, though.