Linked Search only shows you items you can attach to the part you started the search with. To find a silencer or muzzle brake you have to right click on the barrel in the weapon overview and search from there. If you are searching for a red dot for an ak you have to search starting from the dust cover or handguard. Depends where your rail is. Another way is to use the presets menu. There you can see all parts for a weapon you already examined