I'm guessing that in order to seriously damage or grenade a pistol, you would have to overcharge a fast powder like Bullseye, by at least .5 grain over max. With a slower powder, like Unique, I bet it would take closer to a full grain over max, before it becomes a hand grenade.
You'd guess wrong. I've considered carefully before coming out-of-the-woodwork so to speak. To admit to a major mistake that cost me my first handgun. It was a Ruger blackhawk in .357 mag. Some would say it's impossible to destroy a Ruger blackhawk, but I did!
Here's the story, with a lesson or three; This was my first attempt to reload anything other than shotgun shells, or high power rifle. My reloading experience was maybe 2 years at that time. I had just bought the Ruger used, it was actually a convertible, 9mm/.357 mag. The gun was barely used by the previous owner. This was around 1973. The price for a box of .357 shells was shocking even then.
I went to the gunshop, bought a box of 158 Hornady swaged lead bullets, dies, primers, then ran out of money. I got home to find that the only powder I could find, (that I had), in the loading manual was HS-6. So I set the Hornady scale to 6.0 grains, max was 8.0 starting was 4.0.
I WAS IN A HURRY! I loaded 6 shells. I went down the RR. tracks to a mound of dirt, fired a couple rem. 158 JHP factory rounds. Then I filled the cylinder with my newly created shells.
BOOM! I couldn't rotate the cylinder, or cock the hammer. Back home, I took the base pin out, then had to drive the fired shell out of the cylinder with a brass punch.
I had to leave for work,(3-11), so the next day I dropped the scale back to 4.0,(or so I thought), loaded 6 more. This was early November, so it was time to go sight in deer rifles. I took the pistol along to do some shooting with it at the range. Dad was along, he wanted to shoot it too. Loaded six, the first one, the cylinder let go, shearing across 2 chambers. The chunk went to my right, where dad HAD BEEN STANDING only seconds before I shot!
The rear sight was gone, the topstrap was bent. The remaining shells did NOT detonate.
I left everything sit right like I left it for several days, while trying to figure out what I did wrong. Finally the third day I took a close look at the Hornady scale. It's the one with the little wires that sit in a sawtooth pattern on the top of the balance beam. The ten grain wire was on
TEN!, not zero! So I was actually dropping 16.0, then 14.0 grains of fast, dense shotgun powder.
Lessons? DON'T BE IN A HURRY! I was anxious to start loading handgun shells. Being young is a hazard in a case like this. Use a powder that fills the case enough so that a double or TRIPLE,(16.0 is 4 times the starting load), charge will overflow the case.
Oh, and the gunshop where I bought the gun sent it in to Ruger. They sold me a factory direct, exact duplicate of the damaged gun, minus the 9mm cly., at their cost!
I asked for that blown cylinder back from Ruger, which they gladly did when sending the new revolver. I kept it, showing others what not to do along with the story behind the kaboom. It seems to have gotten lost, I haven't seen it for 10 years or so. If I ever find it, I'll take some pics, post them here.
Let the chiding begin-------. Anybody else honest enough to admit to a kaboom?