[darkgael]

Let me suggest an idea I used successfully once.
Drill it out.
How to do this and protect the bore?
Get an extended length bit comfortably smaller than the bore that wlll reach the obstruction so that the drill rotation matches up with the direction of the rifling twist.
Create a bushing around the drill rod starting about one half inch from the bit tip. If you use tape, the wrap will be ccw. Run the bit down to the obstruction slowly.t
Take small bites out of the blockage.
Risky if you go too fast but when all else fails.