I had this happen once with when I put an empty fired case into a new gun. Seems the gun it was fired from originally had a slightly larger chamber than my new gun did and the round became stuck in the smaller new chamber. It was stuck so hard that I did not want to risk damage to the extractor. I had to take a wooden dowel rod inserted into the barrel and using a table top, pushed the empty case against the slide to forcible open the slide while pulling on the slide at the same time. Luckily I was dealing with an empty case and not a live round.