One thing I noticed on my 15-22 was it was louder than a same barrel length 10-22, I checked several things and found the S&W is louder due to ONE simple reason:
The barrel is threaded correct, HOWEVER it's threaded too deep.
I generally thread my 10-22 barrel down to .25, the S&W was .625 or .375 longer .
The S&W folks threaded the barrel to the same depth as a regular AR 15, which means you're losing a lot of the expansion chamber and pretty much screwing the suppressor all the way to the first baffle.
Easiest way to remedy it is by stacking normal AR15 crush washers back to back, in an hourglass config.
To some of you it'll mean nothing, but to me it really made a difference.