I've been running a repro pronged flash hider for so long, the regular gas cylinder nut has gotten away from me.  Just looked through my tool box, no go!  I have way too many small boxes that I don't know the contents of!  Easier to buy another than it is to hunt for it!  I'm definitely going back to the regular muzzle, cause I want to shoot some more of these cast loads!  My gas cylinder has been worked on, the rear ring is enlarged doesn't touch the barrel, when everything is properly tightened to my  done long ago peening.  The inside of this adaptor nut is a cone from the rifle's muzzle to the end, when I look down it it doesn't look well centered in relation to the bore.