To grease or to oil, that is the question.
 

I've just finished putting together my G&P SR16 CQB challenge kit, everything is good to go but I was wondering, about the bolt carrier, what kind of lubricant should I use for it? I have a steel ra-tech bolt inside the aluminum body, I would think I should be using some sort of grease on the outside of the bolt to smoothen out the movement, I assume silicone oil is too light for metal on metal contact. And as for the trigger/hammer/sear what should i use (if anything) to lubricate this? Right now the internals are dry (no lube anywhere) and I have yet to fire it before I clear this up.

Thank you, and have fun shooting each other.

I used graphite powder and white lithium on all metal on metal contact points with all my GBB/Rs

I think some folks like the super lube for metal on metal points.
There are alot of other options tho.
I even heard of a "wax" type lube that provides got friction reduction on metal to metal contact points but doesnt leave gunk that traps dust n grit (i think illusion was talkin about it)

wax, graphite, synthetic grease
oil doesn't necessarily get thick and gunky, but it does run and wash out quickly