I don't understand, what is the 'sinker'? Is the lead ring in the grenade launcher tube? If so it likely won't hurt the rifles accuracy too much but might cause a problem is attempting to use a grenade! Just kidding!! I have been tempted a time or two when a gobbler hangs up just a little beyond shotgun range though.. Still It may be a lead ring or remnants of the firing process, including powder fouling.. I would clean it out just for kicks and because it 'might' be a problem in the future.