I've always found the aluminum free float hand guards to absolutely SOAK up any heat. They get hot as can be. The plastic carbine double heat-shield ones that are cheap, are actually really good. I routinely warm up my hand guards to way past too hot to hold, at which point I will let it cool or last ditch move my support hand to the magazine to save from burning myself.
True story- AR15 barrels get HOT, even after a few shots. I told a friend not to touch a barrel, as it was likely 300-400 plus degrees and scalding hot. He said, "No way, loo...... OUCH!!!!" as he grabbed the barrel and learned first hand.