Years ago I loaded up a couple hundred rounds of .45 Colt cowboy level loads.
The charge was 5.? of 231 and a 250gr RNFP. I fired some and they were not an accurate load. So the rest sat on the shelf for a number of years. Then one winter with nothing much to do I sat on the floor and pulled the last hundred of them down. Poured all the powder in a bowl and then resized the cases.
Then I reloaded the cases using the original 231 but bumped it up to 7.1grs. A much better load.
I use the same technique as jnyork. Powder a tray of cases then carefully inspect them to verify all are the same level. Well somehow this time I missed one. One cartridge with NO powder.
A couple more years passed and I grabbed that box of ammo for that days shoot. I was shooting my 94AE Trapper that day. I filled it up 9 in the tube, one in the chamber and began a semi rapid fire session.
About the third round in the string it went click. Nothing. I ejected the "dud" round and for the first time in this rifles history the live round on the carrier came out with it. I stopped and looked at the floor, saw the three empties and the live round. Picked up the live round, loaded it into the chamber and ........ and ........ the bolt would not close. I had a brain fanny burp and couldn't understand what had happened. I ejected that round and tried to chamber the next one. Nope the cartridge would not allow the bolt to close.
By this time the brain was beginning to realize somethings wrong here. Stop, unload the magazine and lets start checking things out.
Unloaded it through the loading gate. Counted 10 cases, 7 loaded, three empty. But then I noticed only two holes in the target.
Finally like a camera flash bulb the muddy headed stupids evaporated and I realized what had happened. I had a dud. I had a bullet stuck partially in the rifling and partially in the chamber. Had that bullet been pushed all the way into the rifling I would have blown that gun up. Stupid me I tried to blow that gun up by being so muddy headed.
OK enough ranting, here is the bullet that the range master helped me remove from the barrel:

I'm glat it's a hard cast. I'm afraid a softer one might have been pushed further into the barrel. You can see the rifling where it stuck. It only need another 1/8" for the bolt to close. It scared me when I realized just how close to a KABOOM I had been.
Being cautious when reloading is a must. Even when you have developed a technique.
I keep that bullet by my powder scale as a reminder.
Joe