AKA not milspec by any means.US8938903B2 - Firearm barrel having cartridge chamber preparation facilitating efficient cartridge case extraction and protection against premature bolt failure - Google Patents
To permit ease and efficiency for the extraction of spent cartridge cases from the cartridge chamber of a firearm barrel within a wide range of temperature conditions, the internal tapered surface of the body region of a cartridge chamber is prepared by establishing circumferentially spaced...patents.google.com
Larue's stuff works, works great, and his barrels are very accurate. Aside from his marketing hijinks, Mark does a lot to help raise money for 2nd Amendment causes and most recently the battle against the Dems trying to steal this election. Mark IMO is a great American.