I don't have a newer GoPro, but I do have the 3+. I use it for much of the footage for my YouTube channel.
One of the biggest decisions is where to mount the camera. It usually boils down to 3 places. Two are obvious, either on your head, or on the gun. There is one more place I'll talk about later.
We've all watched the videos taken with a Go Pro. We often see skiing or motocycle videos, where the camera is mounted on the side of a helmet. With the side of the helmet in view at the side of the shot frame, it makes the video appear to be steadier, because the side of the helmet doesn't move in the frame of the shot. These videos are easier to watch. When a camera is mounted without anything in view at the side or top or bottom, the video appears to more shaky and harder to watch.
So keeping these two styles of shots in mind (a steady object in frame or no steady object in frame) let's look at the options for hunters, gun mount vs. head mount.
With the camera mounted on the gun, the shot will appear much steadier and the target will be captured in the shot, but you won't be able to capture working dogs, hunting buddies with the camera, without pointing the gun at them. It is also a little more difficult to operate the camera to start and stop. I rarely use this type mount.
With the head mount, the video will be very shaky to watch as your head is on a swivel looking around but it. Just a few seconds of watching this can become uncomfortable to watch. It is easier to operate the camera, though. Editing software can eliminate much of the extra shaking by shortening clips and help make the video a little smoother to watch.
The other option is a backpack type mount. This way of mounting requires a way to remotely operate the camera. With this mount, you will have your head in frame of the camera shot to make the video easier to watch, and you will still have the ability to get dogs and friends on camera safely. This mount is cumbersome to use if hunting near trees, but great for open field. You can make one from a cheap backpack and pvc or buy one. (There is a link in the description of my YouTube videos )
I use multiple cameras to make videos. Here is a link where you can see what the backpack mounts look like, but only a few video clips of it in use.