I know from sad experience that WD-40 will deactivate a primer. I cleaned my cases with it once. I worked really well for cleaning them, but when I had a shot at an elk, it just went "click".
I have a lifetime supply of Kroil "The oil that creeps". I think soaking the barrel in that for a while would make it easier. I hope never to have one stuck like that. I always try to run my hunting rounds through the chamber before the hunt to prevent doo doo from happening on the hunt. There are a million other things that can go wrong, but that one is preventable.