I have failed to charge cases a couple of times over the years. One instance that still sends chills up my spine was when I took a kid to the range with me to burn up some old 38 Specials. Like a kid he was more interested in how fast he could fire them than accuracy. After a couple of cylinders full, I told him to try for the bulleye. 2nd shot I heard a "puff" instead of bang. I looked up and he had recocked it and was aiming. I hollered STOP and he did. Sure enough, the primer had pushed a bullet through the forcing cone just enough to allow the cylinder to rotate.
My normal procedure is to charge the cases in my tray, then hold them under a desk lamp so I can see the powder charge and compare the volume in each case with the two on either side. You can detect even pretty small variations in powder level that way.
