Something that I've had some success with is making sure the rifle is secure, clamping a set of Vise Grips on the cleaning rod, then whacking the hell out of the Vise Grips with a hammer to get the rod moving/reversed.
If push comes to shove on this, a trick that someone here on the Hide did years ago to resolve this same issue struck me as absolutely brilliant; ASSuming that the muzzle is threaded, have a machinist make a cap with a closed end... then drill/tap the closed end for a grease zerk. Then use a grease gun to utilize hydraulic pressure to push the rod back out the breech end.
As I recall, the situation where the above approach was taken was one where a variety of other approaches had already failed and it was looking like the barrel might be trashed. However, when it was finally all said and done, no damage had been done, and the barrel shot fine.