My own design, works very well, just a little louder than my 9mm with sub-sonic ammo.
Not sure how much of what I am hearing is the gas system.
I will close it off and see how that sounds when I get more ammo.

Pretty happy with it, have to tweak the gas port so the bolt will hold open on the last round.

Being an integral design it's only 18.5" long and no SBR tax.

Posted a pic at the end of the sticky at the top of this page.