42-line siege gun M1877 (Russian: 42-линейная пушка образца 1877 года) was a siege gun used by the Russian Imperial Army in late 19th and early 20th centuries. The word "line" in the designation refers to a measurement unit which equals 0.1 inch. Curiously, the "model year" was not the year when the weapon was designed or standardized, but the year when a new rifling system was adopted.
The gun was initially developed by the German arms manufacturer Krupp and was based on an earlier 105 mm piece and would have a typical Krupp horizontal sliding wedge breech block. The 105 mm weapon was demonstrated to a group of Russian Army officers along with a 120 mm design. The delegation liked the 105 mm weapon, but wanted Krupp to change the caliber to a traditional Russian caliber of "42 lines" (106.7 mm). Later the weapon entered production in Russia; it remained in production until 1903.
The 42-line siege gun M1877 could fire high explosive (HE) or shrapnel shells of 15.6 kg (34.3 lbs) weight at a distance of 9.6 km (6 miles).
The gun saw action in the Russo-Japanese War like in the defense of the Nanshan Hill during the battle of Nanshan. The Japanese Army successfully attacked the hill and captured several 42-line siege guns. Due to the lack of heavy artillery the Japanese took the guns in service during the rest of the conflict.
Montenegro used a few guns of this type up to World War I and Finland used weapons of this type until the World War II Era. Many of the 42-line siege guns were captured by the Imperial German Army and reissued to nine Landwehr Foot Artillery Battalions, equipping 22 Batteries.