I picked up a 10/22 charger as a suppressor host. I found that even with its 8" barrel, all the bulk ammo varieties I had laying around were supersonic. That made it noticeably louder than the same ammo out of a suppressed buckmark with a 4" barrel (everything is subsonic out of that). And since they started at just slightly over the the speed of sound, they dropped below the speed of sound quickly and accuracy wasn't great.
After some research, I tried "CCI Standard Velocity Target 22 Long Rifle Ammo 40 Grain Lead Round Nose", It claims 1070 fps, which is slightly subsonic. Out of my 8" barrel, they averaged 1004 fps. They reliably cycle my new 10/22 charger, and they are reliably subsonic. With the suppressor, the cycling action is the primary noise.
Aquila has an option that that's very similar to specs to the cci. I tried it too. The only difference I can tell between them is that the Auila makes a foul smell.
I'll use up my other bulk ammo on the buckmark, and other 22s I have. But the charger will only get these CCIs.
I started with a little box from Cabelas to test with, then bought 5000 rounds for 349 delivered from
targetsports. Its significantly cheaper than 22lr labeled as subsonic. And since its a 40 grain bullet that's barely subsonic, that's about as much energy as I can get.