I think I've had 3 failed primers (that I remember). I always used CCR primers, they were really good that way. I don't know, maybe 3 in 100,000 rounds? I remember 2 at least where there was no powder. Loaders are wonderful things but even the best will hang up once in a while.
All the rest were firing pin problems. I shot an Ithaca a lot, and had to rebuild that link twice in the life of the gun.
The old Smith and Wesson pistols with direct firing pin (rather than a hammer block) tended to break a pin every now and again.
Primers are generally pretty good these days. I use Federal which are great, but I've still had a few issues. Broken firing pins can do it as can ones worn down also. It doesn't take much I guess.
You ever had a squib round? I've been luck and never had one in my sport shooting. I do so much run and gun handgun shooting I'm surprised I haven't. It's not something It want to happen though considering I'm often unloading rounds pretty quickly. My rifle reloads are all hd led and rechecked, precision hand loads, so never had one. I weigh each round after loading and have two check-steps in the loading process.
I've never had a squib round. I've had a couple of 'puffers' but they always got the wad out of the barrel.
We weren't that precise with our shotgun rounds. The doctor that stitched up my eye suggested that I never use dynamite to blow stumps and that I not load shotgun shells. I didn't, but I had a partner that had a high end loader and I'd help him with everything but the actual lever pull.
We would occasionally have a powder charge or a shot load fail to drop. Most of these we'd catch right away but I had at least two make it into my gun with no powder. We used a light charge (.75 oz) and it wasn't easy to tell when the shot was in. I was in charge of gathering and loading the boxes so I KNOW exactly who to blame :)
I have never loaded a shotgun shell, all my ammunition production has been rifle and handgun. I guess the process is the same. Just different.
The biggest difference is the crimp. Gotta have the machine/collets for that.
Yeah, it's different in that way. The projectiles are encased. I don't shoot much shotgun really, so just buy my shells off the shelf.