If someone comes up with more documentation of this incident, I would appreciate it. McNeil's regiment fits. They were there, and they were on provost duty. It just seems like an incident like this would have been noted in various books about the War in Missouri.

I agree about the mechanism of the rifles in use at that time. I have had the unfortunate experience of having powder go off when I though my rifle was empty, so I know it is possible. The last soldier killed in the War Between the States was due to just such an accident when another soldier was cleaning his rifle.