I guy out of Ocala, FL built this one for me about 10 years ago. It's all legit - had to get a trust, do the NFA tax stamp and wait for the form 4 to come back approved - I think it took just under a year to complete the process.
It's a simple design, no Nielson device, so it'll only work on fixed barrel guns/rifles. I have another one for my 9's (PTP tactical) that does have a Nielson integrated to help my Glocks cycle.
On the 22, it works great. The report from the target and the action cycling is louder than the shot itself, so long as I'm using sub-sonic ammo. Standard 40g high velocity .22LRs still make the distinct crack sound going down range.
The 22LR and the .223/5.56 caliber are close enough to all go through the same can, so I can 'suppress' my AR15. But the 3000FPS round make so much noise from the supersonic crack, you still should wear hearing protection (especially if fired under roof).
Suppressed supersonic rounds almost don't make sense...
ETA: Pulled my trust to verify manufacturer of my 22 can. Ron Dishop Silencers