Hi Bob -
You've acquired an original Whitworth gun? Could you fill us in, please!
As to drill, Whitworth said he "always favored muzzle-loaders" and only designed his breech-loader because it was the "fad" in 1860. When he brought out his muzzle-loader he promoted its simplicity of drill compared to the Government breech-loaders (i.e. Armstrong guns). The muzzle-loader would, thus, have a simpler drill than his own breech-loader, but of course he didn't mention that.