The 15cm Kanone 18 series of long-barreled heavy artillery was developed during the German military build-up of the 1930s. The German Army was in need of a long range artillery system firing a 150mm projectile to replace their stock of aged 15cm Kanonr 16 guns of World War 1 origin. Longtime gun supplied Rheinmetall was then given the contract to bring the successor along and this became the 15cm K18.
The K18 was given the rejected carriage design submitted with the 15cm sFH 18 proposal which ended up having the Rheinmetall gun on a Krupp carriage instead. A turntable under the gun allowed the weapon system to be turned a full 360-degrees without having the entire gun and carriage moved in unison. The weapon fired a useful 150mm shell out to ranges of 26,800 yards - further than anything available at the time.
Despite the promising nature of the weapon, focus in production was given to the sFH 18 series of guns which forced the K18 to languish for a time. It did not enter production until 1938 and this only yielded 100 or so examples into 1943. It was soon found that the K18 design was not much better than the K16 it was intended to replace. Its long barrel aided range and accuracy at the expense of making for one heavy and cumbersome artillery piece - it was usually required to remove the barrel for long distance transporting creating two large, heavy pieces to move. The turntable feature also became a time-consuming process to setup and breakdown which added further weight and delays. Gunnery crews were also not fond of the weapon's low rate-of-fire, capable of up to one or two rounds-per-minute.
All these factors led to a short production run and limited involvement in the war. This led to many seeing static action as coastal guns where there range proved excellent and all the complaints about weight and time-consuming assembly/disassembly were nullified.
The K18 featured a travel weight of 41,000lbs and this decreased to 27,500lbs when setup to fire. Overall length was 28 feet with the barrel measuring 27 feet long. Official caliber was 149.1mm though this was rounded up to 150mm (15cm). The weapon utilized a horizontal breech block for unloading spent shell casings and loading fresh projectiles with charges. The gun mounting held an inherent elevation range of +43 to -2 degrees for varying attack ranges. Traverse apart from the turntable platform allowed for 10 degree movement left-to-right from center. Muzzle velocity of the exiting 150mm shell was 2,840 feet per second. The gun and mounting hardware sat upon a two-wheeled box trail carriage. A smaller limber axle added two smaller wheels to the assembly.