To All Interested;
Below is a comparison of the rifling patent drawing in #1286, how it would look with six projections, Mikes shell fragment and my rendering of Mike's image. They appear to match , as well as my eye can attempt a match.
Notice the similarity with Cdr. Robert Scott's other invention (not patent) for the Blakely guns.
If you stop and think about Scott's rifling design, it is the only British rifling system that has projections proud of the shell body, save the Woolwich System of copper studs. Please note that I am not sayhing that Cdr. Scott invented this design(as I have no proof) but it is starting to 'quack like a duck'.
Best Regards,
John aka Bart