Thanks Peter and thedecepticon.
I know what the slightly odd shaped stars are and im trying to figure out how to fix it
Yousee Baader in their infinite wisdom when they created the MPCC instead of making it a smooth barrel, its got that really annoying step that just so happens to land right in the middle of my compression ring and hence tilting it ever so slightly.
Currently ive tried to fix it with thin strips of aluminium can layered up. although this works pretty well. its not perfect. I have even thought about putting the MPCC in the lathe and milling the top shoulder off so it can sit flush. but thats a drastic move.
Thanks once again