Get a steel cleaning rod and a JB a drill bit to it. Put it down the barrel and slowly drill a hole into the jag as deep as you can.
Once hole is drilled use the other end of the cleaning rod and cover it with JB weld and insert into the drilled holes.
Let set.
Spray kroil down the barrel and heat the section with the stuck jag with a heat gun. Vice grip the cleaning rod at the muzzle and lever it out slowly.
