I've been trying to figure out a way to keep the Sony a6300 from overheating while recording 4k video. My copy will typically get through one recording session of about 30 minutes. However, when you restart to continue, the camera could overheat within 15 minutes. In other words, I wasn't very confident I was going to get an extended recording session out of my Sony a6300. Fortunately, I found the solution.
After doing some aggressive Google searches, I came across information about using a small DC fan that you could place on the back of the unit to cool the camera down. It sounded great, but I really didn't think it'd be very elegant. So I decided to see if you could passively cool the system by increasing the surface area in contact with the body to dissipate heat better.
With some searching, I stumbled on the smallrig cage for the a6300. It not only adds rigidity to the camera, but it offers the ability to add several adapters very easily. Important to us however, is the fact that it's made of a solid piece of aluminum. This will allow the heat to transfer around the cage.
I ran about 6 sessions using the cage. I was able to get through 6-30 minutes sessions without the camera completely overheating (I had it powered externally as well). I did however, switch out the battery once during the test. I also left the battery cage door open to help dissipate heat from that area. I noticed that the cage itself did get warm, which is exactly what I wanted to happen.
If you're looking for a way to extend the recording time of your camera, I recommend grabbing this cage. Just keep in mind to leave the battery compartment open as well as swap with a fresh cold battery once or twice depending on your session.