You mean so you can easily fit a 30 cal in a small frame ar without a new mag system.
I use mine for thermaling. Trust me, subsonics suck. Unless you hit a central nervous system component they are running off. I’ve gone to 150 grain gamekings at 1800 fps, makes way more blood and I don’t have 50% of them running off anymore.
Oh, and the subsonics are still loud, the pigs aren’t going to just hang around waiting on you to shoot a second standing still.
You can also easily watch them die with a supper sonic and you don’t have to watch as many run off.