They are not restricted to any particular weapon, but they are perfectly trained in every variety of weapons. Options may come from submachine guns or auto shotguns, for assaulting enemy formations and killing, to rocket launchers and explosive packs for a Rambo-esque demolition against a given place. Whichever they choose freely from the WEC arsenal.
Only 0.0025% of the entire Consortium population have become Silencers. They are the only of the WEC soldiers, who, during their adolescent years, are identified through tests. Then they are enrolled in a specialized military facility, educated in all the intricacies of combat and mission strategies (ancient martial arts, information extraction methods, survival techniques and target elimination).
They are enlisted for life, as most never survive past the age of 40. Those that do move on to positions within the training facility. Silencers have an unlimited lifetime supply of credits. 
Between the applicant screening and psych-conditioning, Silencers are completely loyal to the Consortium for life. During their psychological training, all references to personal history and past interpersonal relationships are eliminated. They have no contact with the world outside the WEC and usually they don't belong to a family.