I'll be honest, 120db was an exaggeration because it was VERY loud, I would not have had a way to measure it in combat gear. Additionally, earplugs are part of a military uniform at a lot of bases so you are required to carry them and the onus would be on you. At that point in time, I was not required to have hearing protection however.

You're not a civilian while enlisted, suing for any reason is not an option in most cases. It's more likely you would file to collect disability in the event of hearing damage after you get out.