When I was shooting competition pistol I would load 4 to 5 thousand rounds in a season. All 38special, for that quantity I used a Dillon press and had my share of backwards primers and backwards bullets. Primers were easy to spot and with 148gr wadcutters backwards didn't seem to make much difference. Never had a problem with double charges, but I did shoot on a line with one fellow who managed to TRIPLE charge the regular 3gr of W231. The first time he scared the hell out of everyone on the line.
And he did it more than once... thus getting the nickname 9grain Joe - for some reason no one was interested in his guns when he decided to stop shooting
Less scary was the no charge round... since almost everyone used revolvers, a no powder charge would usually bridge the cylinder and forcing cone.. preventing the gun from cocking for another shot, that was common enough that one enterprising machinist made pocket money by selling caliber sized brass bullet pushers to force the bullet out of the barrel and back into the cylinder to allow it to be removed.
One of the stranger incidents stemmed from trying to conserve money, I found out that one of the local construction company used 38 cal ramset cartridges, these were identical in size to 38special brass and during one of the Oil Booms, I could get 5 gallon pails of these from the cleanup crews on site. I never did find out what the charge in these were from the factory.. but whatever it was it caused the brass to be so brittle that the cases would split after 2 or 3 loadings, and while a split case was not serious at the load levels used in competition, it was annoying since a regular case could be loaded anywhere from 15 to 20 times. So I learned to leave the ramset brass alone.
At any rate, even when making lots of rounds, being careful when reloading is a habit that pays off.
I have to admit the experience was fun and far more enjoyable than working with High hazard fireworks, which could do serious damage with a misfire.
Paying attention is always a great idea, no matter what you do.