This is me shooting a pal’s .450x3.25" BPE double rifle, an English ‘Best Gun’ made by James Purdey at the end of the 19th century.
http://www.youtube.com/watch?v=NbatynKG1Sw
There are two parts to the sequence - one with a low nitro load, and the other with a half-load of black powder.
Even the smaller BP charge developed 3100 ft lbs of muzzle energy.
tac