My first squib

[halfmoonclip]

My introduction to squibs was a .45 reload, in an effort to develop a light load. One shot (Smith 645) sounded odd, and short cycled. Racked in another round, and this one kicked. Yes, it ringed the barrel, still have it in the shop. Learned my lesson, I hope.
A buddy grenaded a 3" M60, with his own reloads. It was Bullseye. Blew out the top strap, and 1/3 of the cylinder. He contacted Smith; they said a double charge wouldn't blow up the gun, and a triple won't fit. Smith was supportive about getting him a replacement, though it wasn't free.
Personal theory, it wasn't too much powder, but perhaps too little. The guy ran out of primers, and loaded some rounds without them. They doubtless dribbled powder until he seated primers. Ever hear of detonation with Bullseye? Apparently it can't be replicated in the lab, but a combination of a small charge in a big case has been known to do strange things.
Have a long suffering Dillon 550, with a retrofit positive powder return. Never had a powder charge hang up, but as a PP noted, something that interrupts things (a primer draw thru, split case, whatever) you have to patiently get things back in order, so a charge isn't skipped or doubled.
Moon

 

[Will M]

I once bought plated target bullets that had long bearing surface for my Model 19. I loaded according to the directions that was with the bullets. I got one that stuck in the barrel unnoticed, fired another round and noticed increased recoil. Didn't think much iof it until I got home and began cleaning the bore. It now had a noticeable barrel bulge. The revolver was minty until this happened. I would up selling it even though it still shot okay.