Paul810,
Just an FYI....multiple post shooting investigations show that in a shootout, the shooter has reported hearing 'pops'. Turns out they are the gun firing.....I do not remember exactly how it happens but under that level of stress, the body's physiological defense mechanisms 'close down' (if that can be used loosely) our hearing for some reason....

On a range the sound can/is deafening....literally and figuratively. In real life......it seems we may barely notice it.

I'll have to break out my copy of Stressfire to find the exact explanation of how/why this happens...