It's just the 12.5" compact version of the A3, which the AUGA3XS is based off.
Here's a video of a guy in a blue jump suit shooting one in 5.56.
Steyr AUG A3 - YouTube
Agreed that rail adapter is horrid... otherwise, looks perfect.
P.S.
Even the old A1 9mm could be quickly and easily converted to fire 5.56, 9mm is mainly an option for law enforcement where over penetration is a concern vs military where its practically a requirement.