I second the 7/16 inch socket. I dang near let my breech plug sieze up on my new KRB. When I shot it every 10 shots or so I backed it off and everything was fine. After the gun cooled down before I got home it got stuck. I cracked the breech plug wrench trying to loosen it. I've always taken them out at the range while the gun is still warm at the end of the day but got lazy.