What you are actually seeing in the pics are a M16A1s and XM16E1s with suppressors mounted. Here is a picture of an XM16E1 with a suppressor. Notice the partial-fence lower and 603 upper (no forge codes). The description calls it a M16A1, but that is incorrect.
http://i100.photobucket.com/albums/m...pshkfdweri.png
605s were produced in very limited numbers and never saw any wide scale use in the field by Military Forces due to its
unreliable operation. 605s mostly saw their limited service time with the SEALs, until it was replaced with the Model XM607 and, subsequently, the XM177.