There's a world of difference between shooting anything under the hard canopy of an established range and shooting "out in the open". Under a canopy like most good ranges have, the sound is trapped and reverberates all around you, bouncing off the walls and ceiling. In one case, I was shooting at a special rifle range at S&W and we were in essentially a concrete tube with five open shooting positions. We ended up having to "double muff" (plugs and muffs) because all the sound was directed back at us in that confined area. In the open, however, things are quite different.
I wouldn't recommend doing this as a regular practice, but you might try it some time. When you're alone at your range, step out of the covered area and walk far enough away from it so that it won't trap the sound. Try shooting one round without muffs in the open and you'll be surprised as to just how much less impact the sound makes.
Case in point, at Camp Perry, where there are over 150 guys on the line during the M1 Garand match, I was standing right on the line behind my buddy preparing for my match. During the "rapid fire" sessions (10 rounds in 60 seconds) I decided that I had to hear what it was like to be on a battle field with all those rifles going off. I carefully removed my plugs and experienced the sounds of a battle where all 150 rifles were firing all at once in rapid succession. I was SHOCKED to hear how dispersed the sound was! And, I was NOT experiencing any adrenaline rush, either. It was NOT the awful cacophony that you'd expect at all. Instead it was a stream of steady, powerful reports not unlike a good fireworks show. Now, would I do it again? No. I'm sure that the range officer (very serious fellow there) would scold me but it was quite the experience.
Now, I'll also tell you that I had this discussion with some vets there and found out that the #1 Veteran health issue in this country is.......loss of hearing. So, continued shooting without ear protection...especially with fellas close on both sides of you, will most certainly harm your hearing. It's just very different in the field than under a hard canopy.
I'll ALWAYS remember what that meet sounded like. It was like nothing else.
Rome