I sold my MAC-10 9mm select fire and kept the silencer. I still have about 25 mags, a few COBRAY and the rest Walther MPL/MPS mags.
I have a shoulder rig for the Mini-Uzi, it fits the MAC just fine. With the can on it, it sticks out below a sports coat 1 or 2 inches, works great below a Field Jacket.
You couldn't buy sub sonic ammo in the early 80's, so my reloads were Sierra TournamentMaster 130 grain FMJ. Later I found a few thousand Hornady Soft HP 158 gr. (Accurate Powder's big red loading manual Has data!) But I'd say my most common load was a Lee 124 grain cast RN, I must have shot 25,000-30,000 of them!
I have a 1/3 Life size man steel silhouette, with the can on and Sub-sonic loads, a 3 to 5 round burst sounds like a school bell ringing for recess to be over. @ 50 yards: Wire Stock extended, Can on, and kneeling I got consistent 5" groups. When firing like a handgun (two hands) ONE HIT in 2 or 3 bursts was normal.
There were 3 different silencers made for MAC-10's. one for 380. one for 9mm, and one for 45ACP. They were a technology of the 60's and are heavy and over size by today's standards, but apples to apples they are much quieter than anything I encounter today! I made adapters for my 9mm can to shoot it on Mini-14s and AR-15s. With 55 grain Ball ammo It sounds like you are firing High Velocity 22LR. With a tuned lot of ammo, I would get 3" groups at 214 yards (Tom Reyner's closest target in Southern Ohio!) and was the quietest gun with standard velocity ammo!
Ivan