I am surely no expert.But i agree it is a defective barrel.I say this from the condition of the gun.It looks like it has been shot very little.I suspect that the 70 or so rounds I put thru it were more than had been shot befor.

I was pretty much a average gun owner for many years till i started casting my own bullets about 8 years ago.This is when i started learning more about the things that can be and are wrong with my guns.This chip was not there when i bought this gun.But it showed up realy quick.I have had it for several years still makes me sick when i get it out.