It has a lot to do with the camera, microphone, and what you have things set at. Consumer electronic equipment doesn't have the volume range of human hearing. Consumer electronics is set up to record human voices and will never be able to accurately record the full maximum sound level that you can see from a very loud firearm. The cameras have compressors that cut off the loudest noises. Professional cameras have volume settings on the microphone input channels, so you can throttle down the sound. Its like putting hearing protectors on, if you dial the incoming volume down to pick up the firing noise accurately, then you would not be able to hear the low end sounds like voices etc. Add all the above to the fact that consumer electronics have shitty microphones to start out with.
When you play back the sounds from the video, you would need a powerful amp and huge speakers to replicate the loudness and volume of a firearm discharge. Your computer speakers can't do it, so that is why all the videos sound fake. Shitty equipment and recording.
