The Vicksburg reference was not referenced to any 1800s description, it seems to be a second hand idea. Lighting a fuse and rolling it down a hill seems too awkward and unreliable to explode exactly when and where you'd want it too. Plus, on imperfect ground, with bumps, rocks, stumps, limbs, etc. a barrel could easily lose direction or get stuck in the wrong place. A lanyard firing mechanism, say with a primer, would insure a little safety to the men using it and give a better performance against a target.

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David Upton