ben that is a rt rail with a classic valve and emag body. sounds like you are missing the twistlock pin assembly. look down the breach and see if there is a little pin sticking up from the bottom of the breach.
also make sure that there is a rail bushing inside the rear frame screw hole. because the rt rail is drilled out to use larger field strip screw it will need the normal am/mm rail bushing as well as the frame bushing to shoot correctly. shoot me a pm if you questions.