Ordnance Pamphlet No. 127 — United States Naval Guns, Their Marks and Modifications is the Bureau of Ordnance’s standard reference for identifying every gun in U.S. Navy service by caliber, type, mark, and modification. First issued in December 1916 and revised three times over four decades, the pamphlet tracks forty years of naval ordnance development — from the guns of World War I through the postwar era of the Cold War Navy.
Four complete editions are presented here. Use the edition buttons at bottom-right to switch between them.
- 1st Edition (December 1916, Revised January 1918) — World War I-era guns; covers the full range from small-caliber to battleship ordnance.
- 2nd Revision (June 1924) — Post-war consolidation; updated marks and modifications through the early 1920s.
- 3rd Revision (April 1942) — Wartime edition; comprehensive listing of all guns in service at the outbreak of World War II, 145 pages.
- 4th Revision (31 August 1956) — Service guns only; organized by section from Cal. .50 through 16-inch, 14 caliber sections.
Using the viewer: Use the edition buttons (bottom-right) to switch between the four OP 127 editions. The Full Table of Contents button opens a drawer with section navigation for the 1956 edition.