Fig. 20
The use of these guns in the siege was by no means satisfactory, giving neither precision of fire nor extraordinary range, while the gun more often failed by bursting than other types. The principle, however, met with favor and was studied and improved upon.
Another method of applying the rifle principle to heavy guns consisted in casting a segment of a sphere (nearly) on the side of the cylinder part of the shot with corresponding grooves in the bore of the gun, making about one turn in twenty feet. It is somewhat like the principle of the solid musket ball, Fig. 7 with a difference in the shape of the projections, as shown in the annexed Fig. 21, giving the form and size (nearly) of the shot.
Guns of this pattern were adopted for many of the gunboats fitted out by France for operations in the Baltic in 1856, some with four and others with two guns each.
| Fig. 21 | Fig. 22 |
The bore of the gun had a circular section of 6½" diameter with two grooves cut in it, as shown in Fig. 22, which in the length of the bore had a twist equal to one turn in six meters.
| Fig. 23 | Fig. 24 |