By comparison, my AA S410 ERB .22 with full-sized shrouded barrel is a littel quieter than my BSA Scorpion Carbine .177 with shrouded barrel. So I conclude that perhaps it is the carbine / short barrel, and not the BSA vs AA model that accounts to some degree for the difference. And in general, for the same rifle, the .22 should be just a bit quieter than the .177 (I have been told). But in my experience, the difference in how loud the AA-S410 is vs. the BSA Scorpion is not that much, and probably not enough to be the deciding factor if you like one rifle better than the other. And for that matter, having shot Gene's FX Cyclone, it isn't very loud, either.