Has anyone ever experienced a problem with a mushroomed center-pin rod on a 629 with a 3inch barrel deforming? A friend of mine has an older 629 with an un-fluted cylinder and back some time ago had a problem opening the cylinder after firing it. When he took the crane apart he discovered the end of the center-pin rod was mushroomed. He apparently used a stone to remove the mushroom and the cylinder worked fine. Just recently he took the 629 out and now it is almost impossible to open the cylinder again, he suspects the same issue. He has another 629 with about 2000 rounds fired and has never had an issue with it. Any ideas what might be happening?