G36C longer barrel inner & outer?

[CrAzY CH13F]

hey community, looking to get a prometheus 6.03 for my G36C but i want to get a slight outer barrel extension which can support a longer inner barrel and flash hider or change to silencer. ive been looking around and im not sure exactly what to get.

for the outer barrel im not sure what barrel extension to get apart from possibly a G36K outer barrel. with added flash hider/ silencer im not sure how long the inner barrel will be either. would anybody be able to help me out here?

pm me about info or post on here.

thanks in advance for anyone's help.