I did much the same thing once when spark eroding the spike out of a 6 pounder cannon touch hole.

No problems until it broke through to the bore when the paraffin I was pumping down the electrode carburated going off with a dull thump.

Wouldn't have minded, but on hearing the hiss and crackle as it broke through I was shining my torch down the end.

No eyebrow loss, just made me jump.

Tried to make it do it again but no luck :naughty: