I'm truly scratching my head (at the same time I'm kicking my posterior) over it Coffinmaker. Neither I nor anyone else on the posse noticed a squib. As you say, they're hard to miss with BP - either you get thunder and smoke, or NADA.
I did have an odd occurence in the string, but can't figure out how it resulted in a bullet stuck in the bore.
1. Loaded 10 rounds, all with bullets in place
2. In the middle of the string, one round wouldn't chamber - lifter wouldn't rise.
3. Looked into lifter and saw a case with no bullet, and the next round had partially entered the lifter, blocking it's rise.
4. Took a screwdriver and pushed the "next" cartridge back into the magazine, raised the cartridge with no bullet, chambered and then
ejected it.
5. Proceeded to shoot the string.
The only thing I can figure is that the bullet set back into the case (maybe I got a smokeless round mixed in with the BP ammo so there was room for this), and then slid forward into the chamber when I chambered and extracted the brass. But even then, it should have blocked the chamber so the next round wouldn't enter.
I'm so confused..............