I used the blue shit, like Chief Redbeard said.
As far as heat, I dunno, I've noticed my DPMS AR10 doesn't run near as hot as my AR15. I don't know if that has to do with my rate of fire or what not, but that's my guess. I'll finger bang my AR-15 until the whole fucking barrel is smoking, whereas the AR10 I put a scope on it and have been taking carefully aimed shots. I really don't see it as a rapid fire weapon, or at least one that I would be using for extended rapid fire.