I have experienced this problem with my Yugo as well, my problem was a gas leak. What happened to me is when the gun was fired, gases leaked around the top of my Tapco gas tube (the original worked fine), reducing the amount of pressure on the bolt so much that the bolt does not go back all the way, since it does not go back all the way, the empty casing does not have a chance to eject yet, the empty casing is then jammed right back into the the barrel. You should know that when a round is fired the casing expands larger than its original size, brass casings shrink back slightly once they cool, but steel casings do not shrink back. So that expanded steel casing is getting jammed right back into the barrel, I could only get the bolt back open by hitting it on my bench. Check out the "Yugo gas system fix" under the Yugo forum it is one of the top ones in bold.