I had a chain fire in the Lemat revolver that I purchased recently. I was not the one firing the revolver at the time but I did load and cap the gun. It was the first cylinder full that been fired through it since I bought it a couple weeks ago. The chain fire occurred on the 8th shot and caused the out of battery discharge in the 9th chamber. It was easy to figure out as soon as it happened.... the double boom and the fact that the loading lever was hanging down below the barrel where it does not belong made it obvious what had happened. The out of battery discharge fro the chamber on the left side of the barrel had struck the loading lever forcing it downward and breaking the loading lever retainer spring. (see the photo below)
I am confident I also know what caused the chain fire although if I hadn't witnessed it and loaded the gun myself I might not have believed it.
The first two caps I placed on the nipples were #10 Remington and fit loose so I pinched the a little and then went to my range bag and found a tin of CCI #10 caps. The CCI caps fit much better so I capped the remaining 7 nipples with caps that fit. I am positive that the chain fire occurred on the chambers with the loose caps.
I have always been skeptical of chain fires that originate from the nipple end. This incident has changed my thinking a little on the subject. Since I was the one who loaded the revolver, and was watching carefully as my son fired the revolver I'm sure of my conclusion. I loaded the gun in the house since it was cold and windy and wanted to be sure to do an adequate job. Each chamber was loaded with 25 grains 3F Goex a lubed wad and a .454 round ball. There was no spilled powder (I use a measure with a funnel attached) and the wads were new and not dried out. The .454 balls shaved a nice ring of lead as they were seated. I did not cap the nipples until I arrived at the shooting area. I fired the first 5 shots and handed the Lemat to my son to fire off the last four. The chain fire happened on the third shot which emptied the last two chambers. I'm sure the pinched cap allowed flame to penetrate underneath it which ignited the cap and fired the out of battery chamber.
After the chain fire I loaded the revolver a couple more times but had to remove the loading lever in order to fire the gun after reloading. The next two cylinders (18 shots) were fired without incident.