It appears that only two guns were delivered during the war, although a total of nine guns and two spare barrels had been ordered. In the Spring of 1918 they equipped the Third and Fourth Companies, each with one gun, of the 1st Heavy Artillery Regiment. Photographic evidence shows one gun near Dornbirn, Austria on the Italian Front and the other was near Reifenberg, Germany.
Only four more guns were under construction when the war ended. Škoda completed all of these by the end of 1921 as the new Czechoslovak Army decided to buy them. When the Czechs mobilized during the Munich Crisis, the guns formed the Fifth and Sixth Batteries of the Third Battalion of Artillery Regiment 301, each battery with 2 guns, the two remaining guns being held in reserve. Nazi Germany bought all six of these weapons, the spare barrel and all their electric trucks, after the Munich Agreement in January 1939 for a price of over 55 million crowns.
The M. 16 was known as the schwere 24 cm Kanone(t) in German service. They did not participate in the Invasion of Poland, but were assigned only to the Second Battalion of Artillery Regiment 84, where they formed three two-gun batteries. The battalion fought on the Somme during the Battle of France. A second reserve barrel was ordered on 31 July 1940 for delivery on 28 February 1942. For the rest of 1940 and until May 1941 the battalion was emplaced on Cap-Gris-Nez in the Pas de Calais to interdict British coastal convoys in the English Channel and to protect German ones. During Operation Barbarossa the battalion was assigned to Army Group North and fought in the Siege of Leningrad, between January and June 1942, part-way through the siege, all six guns had to returned to Škoda for repair and retubing. This was delayed when barrel Nr. 8 ruptured on 10 December 1942 and a number of roughly-machined barrel ingots in storage since 1918 proved to substandard. The first two guns to be refitted were shipped to the battalion on 18 July 1943, but the rest were further delayed. The next pair of guns were shipped to the front on 11 January 1945. The battalion remained with Army Group North for the rest of the war until its surrender in the Courland Pocket at the end of the war.