A Flaming Empty

[tjwatty]

A year or so back my son was trap shooting and had a similar experience with Nobel trap loads in his Browning Gold. The chamber was belching flame long after the empty was ejected. He used my reloads and I used the rest of the Nobels in my o/u and we didn't have another instance, I did wait a little longer to open the gun just in case.
My theory was damp powder, making for a slow burn, but I have nothing to base my opinion on. I seem to remember 105 cannon powder that got a little damp burning slower but that stuff wasn't smokeless shotgun powder. Definatly some kind of contamination though huh!