I posted to this forum a while back after an incident which resulted with my Ruger GP100 being destroyed. Just for informational purposes, I worked with the ammunition manufacturer and ended up sending them the weapon, Ammo used, spent cartridges, and a full detailed report on what happened and when. They are replacing the GP100 for me. Their ballistics engineer called me and sent photos of the barrel after their machine shop milled it in half to see inside. My incident involved a friend firing two cylinders of .38 special ammo and then I loaded three .357 loads. The gun exploded on the first .357 shot sending parts flying and slightly injuring two people. I was standing several feet away with ear muffs on as my friend fired the weapon. He commented he was not hitting the target but only make that comment once. Nothing flagged the situation for me and I am an experienced shooter. On the first .357 shot, I felt metal fragments hit me like pepper. The shooter actually tried to squeeze off another shot but the gun was destroyed and would not function. Shooter said besides not hitting the target, he did not know the gun had blown up. GP100 is a well built weapon. It amazed me when ammunition manufacturer ballistics Engineer called me to tell me that there were 12 .38 slugs in the barrel. The .357 was only 1/4" into the barrel and the high powered round blew the cylinder and bent almost every part on the gun. A gun smith had to saw the gun apart to remove the two live rounds left in it before I could ship it. I was not shooting the weapon but the buddy has shot high powered pistols before, but not a regular shooter. My brain was not processing that there was a problem and the shooter kept shooting. The gun reported on each shot. The only indication I had was that he commented he was not hitting the target. The ear muffs I was wearing, and not being the shooter, probably kept me from identifying the problem and the shooter failed to identify it either. 12 .38's in a 6" Ruger GP100 barrel and one .357 mag. Nothing bad happens until you deadhead the cylinder and then all hell breaks loose. Never happened to me before and I am 62 years old. The ammunition manufacturer says they see more .38 cal squibs than ANY other ammo. When I asked him if he they saw .357 squibs, he said rarely. He said a new gun is more likely to squib a slug if its short on powder which can and does happen because the bore to slug fit is tighter. When asked what revolvers squib the least, he said any MAG's. I will only shoot .357 ammo in the replacement Gp100. The chance of those loads squibing is magnitudes less according to the ballistics engineer. Never stop learning, but this one scared the heck out of me not to mention my close friend and his wife who suffered minor cuts also. We were behind the firing line, two feet behind the shooter. Metal bounced off the frame and went out and back on both sides. Hopefully this might be informational if not interesting. Bob in Ga.