Originally Posted by Nahib_Stilgar
Looks more like an Armotech/Miltec MT66 with their E-trigger.
Edit: Correction, it is a SIM 4 RIS by Arikron
Good call. Hopefully all it needs is the oring for the bolt. Retails for $400 so I am pretty happy with it. Hopefully the previous owner had it setup to have a tank on the back and its not missing any parts.