The BL 4.5 inch had a caliber of 114 mm and it used the Welin Breech. The total weight of the system was 5,261.6 kilograms and the length was about 4.8 meters.
The elevation of the gun was from -5 to 45 degrees and it could traverse up to 30 degrees. The usual amount of people operating the gun was ten and the maximum range was about 20,500 meters. The barrel of the gun was rifled and the gun even featured a recuperator.
The muzzle velocity of the 4.5 inch gun was about 690 meters per second and each shell weighed about 2.7 kilograms. The gun's rate of fire varied between one to two rounds per minute, but generally it was one round per minute. It was also towed by the AEC Matador Tractor and the first model produced was the BL 4.5 inch Medium Gun Mk. I.
The Mk. I was followed by the Mk. II in 1941. There were some slight differences, but overall, they were fundamentally the same. The maximum range was nearly the same for example and the main difference was that they towed on different carriages. The M1 4.5 inch Gun also used the same kind of ammunition as the Mk. I and Mk. II.
The Mk. I was introduced in 1938 to replace the older BL 60 pounder Gun. The 4.5 inch Medium Gun was used from then on to the end of World War II in different places including North Africa and Greece. They were also used in Normandy and even after World War II the Mk. II was being used for training purposes. The only users of the Mk. I and Mk. II Medium guns during World War II were Great Britain and Canada.