I got one stuck in a 243 once that became a big deal getting it out. It took several highly mis-qualifed gunsmiths, a large plumb full snap-on tool chest and an impressive supply of adult beverage to successfully screw up a good Dewey rod and a few other random items trying make it come out. We won't even talk about the unregulated oxygen bottle with 1800 psi in it. 
Let me say this: if you are able to get hold of it good enough to pull on it, only twist "WITH" the rifling while pulling 
We ended up with the barrel off the rifle when it was all said and done. It actually became quite comical as the night progressed, and it still inspires some belly laughs from the participants from time to time.
I like Boresnakes for pistols, shotguns and 22's, but thats about it for me now.
Anyway, good luck
