I went to the range today with the FLIR IR camera and made a few videos of weapons firing and heating up. I shot my Colt 6933 with my M42K 07 on it as well as a few other guns and was surprised as a few things.
First off, the first time I viewed the rifle firing was when it was cold out of the case. I figured the suppressor would heat up from front to rear, but was surprised to see that the can heated up instantly on the rear, (blast baffle) and front (end cap). It took several shots before the suppressor's mid body heated up to the temperature of the front and rear of the can. I can see the reasoning for all inconel baffles after watching the replay. The video I saved, didn't show this in as great of detail as the first one of the day, but if you slow down the video between the first few shots you can see what I am talking about.
Second, not near as much heat builds up in the bolt carrier of the AR as I feel most are led to believe. If you look at the video of the M4, you will see that most of the heat buildup in the receiver area is on the actual gas tube and carrier key. I did a few mag dumps semi, and pulled the carrier and bolt out and inspected it with the camera and still the majority of the heat was on the carrier key itself, not so much the bolt or bolt carrier. I would suspect this heat build up on the carrier is why you see so many problems with improperly staked carrier keys. Not so much from the force of the gas pushing on it, but the extreme temperature difference between the key and bolt carrier. Heating up and cooling down, one piece of metal being a good bit hotter than the other might work the screws loose over time. If you watch the video, you will see the bright glow of the key going back and forth.
Gas pistons, as with the AK do a damn good job of keeping the heat at the end of the gun. I noticed the trunion heating up a good bit after firing, but most of the heat was on the front end.
You can see the M4 cut out heat up first during firing of the M4.
All in all, it was pretty neat seeing things from the prospective the IR camera lets you see. Enjoy the Video's.