Michael, please keep the Lightning in the can until we can do a bit more research. And please don't use it in one of those rare old barrels.
Recently, re-reading a lot of oldish stuff on powder & primers, I came across something written on Lightning by one of the writers of the day. (Whelen? Roberts? Sharpe? Hopefully I can dig it out in a day or two) What the writer wrote was to the effect that many small-bore barrels were ruined by Lightning, with it's extremely high nitroglycerine content (40 %) and that it did not take many shots to ruin a barrel. The old corrosive primers were not the only problem.

Richard