A K5(E) is preserved at the United States Army Ordnance Museum in Maryland. It is composed of parts from two guns that shelled Anzio beachhead during World War II. They were named Robert and Leopold by the Germans, but are better known by their Allied nicknames - Anzio Annie and Anzio Express. When the Germans were forced to retreat, the guns were spiked by their crews. The guns were discovered on a railroad siding in the town of Civitavecchia, on 7 June 1944, shortly after the allies occupied Rome. Robert had been partially destroyed by the gun crew before they surrendered and Leopold was also damaged but not as badly. Both guns were shipped to the U.S. Aberdeen Proving Ground, (Aberdeen, Maryland) where they underwent tests. One complete K5 was made from the two damaged ones, and Leopold remains on display to this day.
The Krupp 28-cm-Kanone 5 (E), in short K5, was a heavy railway gun used by Germany throughout World War II.
The K5 was the result of a crash program launched in the 1930s to develop a force of railway guns to support the Wehrmacht by 1939. K5 development began in 1934 with first testing following in 1936 at the Firing Test Range Rügenwalde-Bad (German: Schießplatz Rügenwalde-Bad) in Farther Pomerania at the South coast of the Baltic Sea. Initial tests were done with a 150 mm barrel under the designation K5M.
Production led to eight guns being in service for the Invasion of France, although problems were encountered with barrel splitting and rectified with changes to the rifling. The guns were then reliable until the end of the war, under the designation K5 Tiefzug 7 mm. Three of them were installed on the English Channel coast to target British shipping in the Channel, and proved successful at this task.
Towards the end of the war, development was done to allow the K5 to fire rocket-assisted projectiles to increase range. Successful implementation was done for firing these from the K5Vz.
A final experiment was to bore out two of the weapons to 310 mm (12.2 in) smoothbore to allow firing of the Peenemünder Pfeilgeschosse arrow shells. The two modified weapons were designated K5 Glatt.
Several other proposals were made to modify or create new models of the K5 which never saw production. In particular, there were a number of plans for a model which could leave the railway by use of specially modified Tiger II tank chassis which would support the mounting box in much the same manner as the railway weapon's two bogies. This project was ended by the defeat of Germany.
The Krupp K5 series were consistent in mounting a 21.5 metres (71 ft) long gun barrel in a fixed mounting with only vertical elevation of the weapon. This gondola was then mounted on a pair of 12-wheel bogies designed to be operated on commercial and military rails built to German standards. This mounting permitted only two degrees of horizontal traverse. The carriage had to be aligned on the rails first, with only minimal fine levelling capable once halted. Hence the gun could only fire at targets tangential to an existing railway track.
To track targets needing greater traverse either a curved length of railway was used with the gun shunted backwards or forwards to aim; a cross-track was laid with the front bogie turned perpendicular to the rest of the gun and moved up and down the cross-track to train the weapon; or for 360 degree traverse, the so-called "Vögele Turntable" could be constructed, consisting of a raised rail section (the "firing bed") carrying the gun, running on a circular track with a central jack to raise the gun during traverse and to take some of the enormous weight.
The main barrel of the K5 is 283 mm (11.1 in) in calibre (caliber), and is rifled with twelve 7 mm (0.28 in) grooves. These were originally 10 mm (0.39 in) deep, but were shallowed to rectify cracking problems.