[stash247]

Black, a solid piece of brass rod, as big as will fit in the bore without binding, and a bit of penetrant, like 'Kroil', would be my first attempt; the rod should be only a couple of inches longer than the barrel, and flat on both ends.
Pour a tablespoon of the penetrant dowh the bore, from the muzzle, and keep the muzzle elevated, for 12 hours or so, before proceeding to attempt to drive out the case, with the rod. If it's simply a stuck case, because of the case having been fired in a different chamber, it will be a walk in the park. The clost fit of the barrel keeps the brass from feexing as you tap on the rod, getting every bit of force to the head of the case; the brass won't harm the bore in any way.
Re read the thread starters original post, if it does not come out and open after six or seven whacks; could be, it's not a stuck case tying up the rifle.
Good luck!