The guns were built by Armstrongs (Elswick Ordnance Company) and were originally intended to be mounted as a pair in a twin turret on the Japanese battleship Yamashiro but the order was not completed.

To adjust more than 2° the entire gun car was moved forward or backward along its track.

The railway mounting was of the "cradle and rolling recoil" type : the gun was mounted high up in a standard cradle with hydropneumatic buffers which allowed the gun to recoil 34-inches on firing at maximum elevation without striking the ground, and the remaining recoil force was expended by allowing the entire railway car to roll backwards 20–30 feet until stopped by its brakes.

King George V personally oversaw the firing of the first shell by Boche Buster from near Marœuil, 6 km NW of Arras, on 8 August in a fireplan to hit German reinforcements being sent south to oppose the British Amiens offensive.

[4] A total of approximately 235 rounds were fired by the guns during their four months on the Western Front.