I tried on 1887 extended mags and grip,and it's hasnot sho me the gun in game,it's means that,for this eapon one of 2 attachments cannot get combo,for example mk14 akimbo,so u didn't do it,cuz in game thereisnot hte gun perk-akimbo,only for secondary eapon
and another,for javelin.grip no work cuz thereis any eapon upgrade such as grip or red dot for rocket laucnher DDDD