I can't remember if they said what/how they managed to get the flat top bit (tbh, I wasn't paying attention)
The rest is like I said, a (modified, obviously) P90 avec le M60 flash-hider et le buttpad pour une L85 (see, I can break languages too!)
Also, the pistol that the Clerics have (the Doc uses one to shoot out the lights) is a TM 4.3 hi-cappa.
The weird pistols that the guards who are holding River (she convinces one that a drawing of on the wall is actually her) have are Glock 26s with the 'advance' muzzlebreak.