i'm not sure what's available in the us. here 9x39 is the most abundant subsonic round with enough "oomph" to put down an obese mutt i guess in the us it would make sense to use something like 300 aac blackout / .50 beowulf / anything subsonic in 7.62 or bigger and use a shorty ar platform for that. machining a generic suppressor is easy, and a chinese hobby lathe is like few hundreds $$$. not a big deal.
Russian Federation