These are, I think you will find, the expanding rivets which were placed there to attach wood bottoms to the projectiles. The wood bottoms have, on projectiles that still have a rivet affixed, either split or rotted away. The use of expanding rivets replaced the use of tin straps, on British ordnance, in the 1860s. Wood bottoms were required with fuzed spherical projectiles, to keep the fuze pointed forward. There were also used with solid shot in brass guns to prevent bore damage. A single rivet in large natures indicates Land Service whilst two smaller rivets meant Sea Service. Below is an extract from an unpublished work, it relates to British artillery Circa 1865:
Common wood bottoms were a disc of wood and the sides were shaped to be either conical, for Gomer chambered ordnance, hemispherical for cylindrical chambers or were left cylindrical for all other ordnance. The nature for which the bottom was intended was stamped on the underside of it. They were hollowed out to accommodate the base of the projectile and common bottoms were fixed with a single central rivet of gun metal. Wood bottoms for naval use were in only 32pr and 8 inch, or 68 pr, size and were all conical shaped. The hollow went completely through the wood bottom, leaving the underside of the shell flush with the lower surface of the bottom. This was necessary to enable the projectiles to be in actual contact with each other when double shotted, it also meant that a single central rivet could not be used to fasten the bottom and so two rivets were instead used, inclined towards the center. Refer also Commentary on page 78.
The navy’s use of wood bottoms in bronze 6 prs with the 4 ounce charge for drill purposes was prohibited because it was found that firing a loose ball with such a small charge did not harm the bore and so wood bottoms were unnecessary.
|