This is what happens with what I believe to have been a double charge of 700x under a 155 gr DEWC. Had a bag of these ( 3.5 grs 700x in 357 brass) loads that I had done up with a Lee loader and then kinda forgot about them after I picked up a cheap JR3 and some dies.
Anyway, the day I got a membership at one of the ranges here, about two years ago, I took these and my SP101 with me to do some draw from concealment practice. Shot about 30 rounds and then loaded up again, fired 2 rounds and then the third fired with a hollow pop boom and massive recoil. Felt like I had just lit off a top end 357 mag round. Had to use a magazine for my mini 30 to hammer the brass out of that chamber. Checked it out, couldn't see any problems, no bulge in barrel and nothing that I could see wrong with the cylinder. Loaded up another cylinder full and fired away with no issues. Brass was slightly sticky coming out of the chambers but everything worked correctly. As far as I could tell. I was pretty new to revolvers and reloading in general so I didn't know what to look for.
Over the next two years I shot it often with full power loads that I made and finished of my buffalo bore rounds that I had bought. Never a problem except intermittent hard extraction if I didn't keep the chambers absolutely spotless.
Fast forward to Thursday two weeks ago, I went to the range and tried to finish off 3 boxes of PMC 158 grain soft points I was given, from the start extraction was impossible, had to hammer the brass out of one chamber every time. After three cylinders full I called it quits and shot something else.
Took it to work the next day and removed the cylinder, cleaned it and put a straight edge over each chamber. Sure enough, the one I had marked with a sharpie the previous day was bulged out a few thousandths. Also found the signs of stressed metal under a good light and magnifying glass. I gotta say Ruger makes a strong revolver because I shot this for two years after it happened and even developed some excellent loads with it. But here's the pictures and even some florescent mag particle pics that I did at work as a bonus.
Also Im pretty darn certain it was not a squib that got hit by the third shot, I remember making two holes in the target and then boom, and even that one made a hole.
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