My first experience was with a blr that had ripped the rim off a 270 live round in chamber. Guy brought it to me and asked for help. My first move was to stop and think for a while. Then I just left it outside because it was -45 degrees out and taped it on butt. Sometimes simple is good
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.
OK... My take here... Many many years ago primer manufacturers starting sealing primers to prevent moisture contamination. When the, later exposed as fake, armorer from Alaska reported misfires to contaminated primers it got a lot of press and people assumed it was real. It turned out to be a hardware failure he wanted to blame on primers.
At that time and once since I soaked 10 primers in WD-40 for several days and then put them in cases and fired them all and not only did they function properly but they also gave me the same accuracy as any other similar load from the same ammo... So... I have absolutely NO problem with worrying about using a penetrating oil in guns.