I think the worst round I've fired was a .22 Mag out of a revolver. That sound has a frequency pitch that could penetrate steel. It felt like an ice pick was suddenly shoved into my ear.One of the worst things I ever did was to fire a Walther model 5 .25 acp without hearing protection. It's not that big a round... is it? I think it was louder than my .45 P-90!