Gotta be 40 years back when I was around 35 I bought a cased detachable lock Westley Richards .577 Nitro, I was in good shape, 5'8" 165 pounds. Two shots were enough, felt like I was in the middle of an earthquake. Sold it immediately to none other than Elmer Keith who wrote me it was a pussycat. Also had an 8 bore double BP about the same time, forget the make but a good one, also violent but didn't seem quite as bad. I now have a 6 bore flintlock rifle by Jover, London, weighs about 10.5, if I can find a 6 bore mould I will get up my courage to try it out, of course I can start with mild charges.