Hey there, Tony here. I'm a part of J4 (I know, right). I just wanted to relate my experience with the Mule.
I had it down in my basement and was shooting it with a JJ stainless barrel one day. It took me a couple of shots to realize that it just wasn't as loud as I was expecting.
Considering it was a stainless barrel and I was in a basement, it should have been fairly loud. But it wasn't anywhere near as loud as I was expecting.
It was actually very quiet, as smooth and quiet as anything that I've shot. Out on the field, even better. It will go toe-to-toe with a Matrix in terms of decibels produced, or lack there of.
And that's all I have to add at this point.