I have a marlin cowboy that had a bump inside the bore under the front sight. It happens when the factory installs the front sight , the barrel is so thin at this point that it caves in. Today i removed the front sight and measured the barrel from the bottom of the sight cut to the bottow of the magazine tube , it measured 1.303. Then i fired a hardcast 400 gr. bullet through it without the sight in and remeasured and it measured 1.3035. Next i fired a solid copper bullet through it and it now measures 1.305 and the bump is gone. I will refit the front sight to prevent this from happening again. :grin: Hope this helps some of you that may have the same problem.
