[Professional Engineer]

I tried some subsonic 223 once. So quiet you didn’t need hearing protection. The RSO thought I had squibs. That stuff did not cycle.

[mylife]

I tried some subsonic 60 grain .22

Works fine in Ruger MK II and 10/22.
It even works in an AR15 with a CMMG 22 conversion kit, but accuracy is reduced.
Will not feed in Marlin 60.