I had an AD w/ an AR indoors when I was selling guns. My ears rang for 3 days afterwards.
I have been to indoor ranges where they allow rifles, and it is damn near unbearable. I don't shoot at them because of the noise levels. Check out your area and see what you can find, maybe you can try it out. Also, the noise level is over time remember. So if there's a 1dB increase for each shot fired, the damage it's doing to your ear is cummulative over time. I'm not a Dr., but I do have a degree in architecture and we had to learn alot about acoustics. It was a few years ago but I seem to remember this. Personally I'm as concerned with damage to my ears as I am with being uncomfortable since I'm still a relatively young 28.
Is your berm at the West end or the East? There might be some things you can do depending on which way it goes.
Alot of the things you deal with in architectural design and passive design come into play with dealing with the elements on a range. That's where my limited expertice comes from.