Expert Gunsmith JC Blauvelt on Over-Pressure Rounds and Exploding Handguns

A note to all you Gun Nuts: These photos came into my inbox attached to the following caption: "For those of you who load your own ammunition... A guy came into our department the other day to ask a favor. He had a Smith & Wesson Model 629 that he wanted to dispose of after a mishap at the range. He said there was a loud bang when he tested his new load and the gun smacked him in the forehead, leaving a nice gash. When the tweety birds cleared, this is what he saw..." Rather than comment on the photos myself, I decided they were serious enough that they deserved something intelligent said about them, so I sent them to my friend and ace pistolsmith John Blauvelt. Click on to see what he had to say. --David Petzal
Begin forwarded message: From: JC Blauvelt
Date: October 30, 2009 8:09:43 PM EST
To: Dave Petzal Subject: BANG Dave, Well you asked for it. I hope you find this useful. Thank you for the opportunity. A graphic reminder of the art of home pressure testing. What I see here is typical of a vastly over- pressure round fired in a revolver. The in- line round of ammunition blew out the top of the cylinder, both adjoining chambers, and removed the top strap. Most of the destroyed revolvers I have seen usually have the top strap of the frame still attached at the front, above the barrel, and it is peeled forward. The weakest point of an adjustable sight revolver frame is the back end of the top strap were the rear sight cut is. In this revolver the whole top strap is gone and most of both adjoining chambers. This points to a very strong pressure spike.
How did it happen? One clue is the reloader's quote that he was "testing his new load." So, it is most likely the reloader's fault. He was either trying to make a "Super Magnum" load beyond the recommended loads or used the wrong powder - i.e. grabbed a can of 231 instead of 296 or possibly changed powders and forgot to change the settings on the powder measure. A barrel obstruction from a squib round? I do not believe so. I do not see any indication of a bulge in the barrel. Unless it was a bullet from a squib round stuck just forward of the back end of the barrel. In any case, these are sobering photos. Look at the amount of shrapnel that let loose. It could have caused grave injuries to the shooter and/or bystanders on either side of him. An expensive lesson learned, and fortunately no one was injured.
For all the millions of rounds of ammunition reloaded each year, it is rare to see this happen. That's why it makes news when it does. Always remember to check, double check, then check one more time that the recipe you are using is correct, wear your safety glasses, and ear protection. Also, in this guy's case, he likely needed a half of a bottle of aspirin for his headache. JC Blauvelt Gunsmith, Inc.
www.JCBgunsmith.com