... Technically naturally it's not possible to crown a thread protector, so I assumed that Dave was asking for a concave Reduce to the end on the thread protector, because that may be what the majority of people indicate when they say "Crown a barrel". The gasoline lock entrance sight http://claytonhylyl.full-design.com/The-Fact-About-clamp-on-suppressor-That-No-One-Is-Suggesting-54315138