I have a lightly used Broad River Tactical Hub/Bravo adapter and SD barrel for CMMG's Radial Delayed Blowback system that will make your supersonic 115-125gr 9mm ammo subsonic.  I've gone another direction with my PCC set ups.

To see what it looks like in action, check out this dude:  https://www.reddit.com/r/NFA/comments/1wkn5au/she_runs/

The barrels are out of stock at BRT's website and take forever to get (ask me how I know).  I'd prefer to sell as a set, but the prices are as following:

$420 shipped for the set

$190 shipped for the HUB adapter

$245 shipped for the barrel