Although the chat has strayed a good deal from the ex-USN 7-inch or 180mm rifles sent to Java, any error made in this forum needs correcting. A friend informed me off-forum that the image of the Panama mount I attached in my previous posting actually shows a 270° mount, not
the 360° standard mount that I specified. When first designed as a temporary or emergency solution to emplace the French GPF 155mm field gun as a coast artillery piece, the Panama mount encompassed a full circle (360°). It quickly occurred that in most situations, the full circle, wherein the split trail of the gun swiveled around to the front and pointed the gun to the rear, was not necessary. Indeed, in not a few wartime photos of 360° Panama mounts, sandbags have been laid across the midpoint of the circle, both to protect the gun crew and serve as a traverse check to prevent the carriage from being rotated unnecessarily far. The immediate answer was a half-circle or 180° Panama mount, with the truncated side facing the water, and one sees frequent examples of such a configuration. Far more rarely built was the 3/4-circle or 270° Panama mount, where the gun in question saw emplacement on a point of land and had to cover more than a planar seafront, but one that “turned the corner” and made necessary the extra quarter-circle.
The best known examples of the 270° Panama mount occurred at the top of a sandy bluff at Fort Funston, HD San Francisco, and named, at least unofficially, Battery Bluff. Because of the severe erosion of the face of the bluff, today those four Panama mounts lie in pieces at its foot.
The 270° Panama mount whose image I included in my previous posting is one of four Panama mounts in the late 1930s emergency battery that protected Sitka Sound and Sitka Naval Air Station. The battery stood on Makhnati Island, the seaward terminal island connected to Japonski Island by a causeway a bit less than two miles in length and crossing seven islands. After war began, Battery Construction 292 for two 6-inch BL rifles reaching 27,000 yards (15+ miles)—versus 19,000 yards (10.8 miles) for the GPF—was undertaken in the same area of Makhnati Island, and in fact required the removal of GPF guns Nos. 2 and 3 and their Panama mounts. Such construction was unusual, in that the army wished to have use of the entire emergency battery until its successor was completed—at a safe, tactically distant site. The limited amount of suitable land available, likely impacted by muskeg and bog forest so prevalent in SE Alaska and NW British Columbia, made this less than ideal solution necessary.
A photo, taken on the same occasion as shown on the one I previously posted, reveals both No. 4 gun mount of the GPF 155mm gun battery and No. 2 shielded 6-inch gun of new Battery Construction 292, appears here: