That is most interesting, Gene.
I wonder if the rifling was cleaned up using a cast lead lap, free to turn in the rifling as it lapped the lands and grooves.
As the enlargement from 11 bore (.750 +?) to 10 bore (19.7 mm = .775)indicates up to 25 thou enlargement I am pleasantly surprised that it still retains its rifling, and would have lost my bet.
The original Victorian proof would have been measured with a plug gauge, and would have been the bore diameter to the top of the lands.
I suppose that it is possible that the 19.7mm may have been measured with a micrometer, and taken from the groove diameter. If so my calculations as to the enlargement of the bore may be over-stated.
The rifling being full length suggests that it was built as a dedicated purpose rifle, rather than being intended to be used like a Paradox with shot as well as bullet.
Last edited by Parabola; 01/24/23 06:23 PM.
