I have seen dozens of firearms- usually .22 rifles, with a "ringed" barrel. Squib load- low powder, bad powder- lodge a bullet into the bore. When a SECOND, normal round is fired- the air compressed by the second bullet creates a raised ring, right behind the stuck bullet.
Happens with factory loads, remanufactured loads, and handloads if you are not careful.
What we have here is... failure- to communicate.