I'll change my inner barrel to 550mm which is 21.65inches and put a 250mm - 335mm suppressor, and put a scope on it.
IMO your M4 is now become a "tactical precision rifle".
Tactical Carbine Certifications Grade
Score 270 to 300 = Carbine Master
Score 240 to 269 = Carbine Marksman
Score 210 to 239 = MEDEVAC
Score 209 or less = K.I.A.