List of British Ordnance Terms - RML

RML

Rifled Muzzle Loading : introduced in British service in the mid-1860s following the unsatisfactory service performance of the Armstrong RBL (rifled breech loading) guns. The inside of the barrel had spiral grooves into which "studs" on the shell fitted, to spin the shell and hence improve accuracy and range. The propellant charge, followed by the projectile, is loaded through the muzzle. "RML" became necessary to distinguish between the new rifled and old unrifled smoothbore muzzle loaders (ML).

The first generation of British RML guns in the mid-1860s typically used William Armstrong's design of a wrought-iron "A" tube surrounded by multiple wrought-iron coils. Later Marks of guns built by the Royal Gun Factory from the late 1860s onward introduced a toughened mild steel "A" tube to increase the gun's strength, and also used fewer but heavier coils to reduce the cost of manufacture. RML guns in British government service were designed by the Royal Gun Factory, Woolwich, and typically had only a few (3 - 9) broad shallow rifling grooves, compared to the many sharp-edged grooves ("polygroove") of the Armstrong system. They were hence referred to as "Woolwich" guns.

In the 1870s "gas checks" were attached to the base of RML shells to seal the bore and reduce windage; it was soon found that these gas checks could also be used to rotate the shell, allowing studs to be dispensed with, which was an improvement as the slots in the shell for studs were found to be weak points leading to shells fracturing. The gas checks evolved into the driving bands still in use today. Modern RML examples are rifled field mortars.

The last recorded active deployment of British RML guns was some RML 2.5 inch Mountain Guns in German East Africa in 1916, although several batteries of RML 9 inch Mk VI high-angle coast defence guns were in service in England throughout World War I.