When I first started loading 38 special at full power, with a swc, got a squib.
I had never crimped anything yet, as I only shot mouse fart loads to this point.
The next bullet in line also had worked forward in the case, and kept the cylinder from turning.
The squib had jumped the gap and just made it fully seated, into the barrel throat.
It could have been pretty nasty. I will never forget that sound, or the feel of that squib.
Gave me quite a scare, when I figured out what had happened, almost quit reloading. Now I crimp all my pistol ammo.