Arming the Empire

Short Magazine Lee–Enfield Mk III

Despite being a naval power first and foremost, the British Empire did not rest when it came to small arms development. Unlike most other nations, they went with a universal short rifle intended for all branches. A decision that brought forth one of the most iconic weapons of the early 20th century.

The "Long Tom" rifles proved to be problematic during the Boer War due to lack of quality control. Despite having large potential when it came to accuracy, sighting issues resulted in many shots falling short, resulting in the British troops being outclassed by a large margin during long-range combat, which was prevalent on the African Veld.

History

Compared to the other Great Powers, the British Empire only had a relatively small standing army.
Whereas France, which had a similar population to Britain in their respective home territories in Europe, fielded almost 800,000 men even during peacetime, the British volunteer force numbered a mere quarter million.
Thus the big push for the adoption of a new magazine loading (and eventually smokeless, after the introduction of Poudre B) rifle came from the Royal Navy intererstingly, ending the almost two decade long dominance of the Martini-Henry single shot rifle the British were carrying since 1871.

Thus, after nine years of trials and development, the Small Arms Commission officially adopted the Rifle, Magazine, Mark I, better known as the Lee-Metford today (In 1891 that name would become part of the official designation) in 1888.
This model paired a bolt and magazine system designed by Scottish arms developer James Paris Lee with a rifling pattern patented by William Harris Metford. Although intended for the newly developed Cordite propelled ammunition, after the adoption the rifle in 1888 was initially given out with black powder cartridges still.

Despite being replaced by the .303 calibre, Rifle, Magazine, Lee–Enfield in 1895 (the main difference being the rifling pattern), the Lee-Metford saw action in the Second Boer War (1899-1902).
The main reason for the changeover to the Enfield pattern of rifling was that, while it faired very well with black powder charges, the new, high velocity Cordite propelled rounds lead to increased barrel wear, demanding action.

The aforementioned Second Boer War then strongly influenced the further development of the Lee-Enfield series. One of the first big changes agreed on was to adopt a charger-loading system similar to what the troops encountered in the South African Veld when faced with the Mauser rifles the Boers used. Their stripper clips gave them a distinct advantage when it came to loading speed, despite only having half the magazine capacity. Many of the older "Long Lees" were later also adapted to this new charger-loading pattern.
The second big change would be the length. Where the infantry complained about their long and cumbersome rifles, the cavalry felt the need for an upgrade for their carbines to be capable of reliably engaging at long range - putting Britain on the path to adopting a universal short rifle for all troop branches.

Further desired changes were:

Lightening of the rifle
A more rugged magazine
A two stage trigger akin to the Mauser
Easier field maintenance and disassembly

The overall action and ergonomics would be carried over, same with features like the long-range dial sights and the magazine cutoff, despite initial doubts about the usefulness of the latter.
In 1901, following first tests with a shortened rifle, trials for a universal short pattern began and by 1904 it was decided that the Short Magazine Lee-Enfield Mk I would become the new service rifle. At a barrel length of 640mm (25.2 inches), it sat halfway between the former rifles and carbines and was well received inspite of concerns over accuracy.
This pattern featured a charger guide that was half-included with the bolt head, a new nosecap similar to the ones used in Mauser 1893 family export patterns, a new bayonet lug that removed the need to have it attached to the barrel directly, but rather an embossing on the front of the nosecap, as well as new sights. Older long rifles were converted to this new pattern as well, becoming known as "India Pattern" rifles.

Unspecified here, there were many iterations in between models of the Lee-Enfield family of rifles. In British nomenclature, these minor iterations that didn't warrant an entirely new designation would be marked with a star, leading to designations like Short Magazine Lee-Enfield Mark I*** - each star representing an additional update to the pattern.

The British were one of only two Great Powers to carry a universal short rifle in 1914, the other being the United States with their Springfield Model of 1903. The advantages of a single rifle for all branches would soon occur to other nations as well like Germany with its Karabiner 98a. However, it would take most other countries until the interwar period to settle on a universal short rifle pattern.

The Pattern 14 rifle was set to replace the SMLE Mk III before the war, but was prevented from doing so by the same. Nevertheless, the British ordered hundreds of thousands of these rifles in the USA. Orders would come out of Winchester, Remington and Remington Eddystone. Despite playing second fiddle to the SMLE for the British, the USA would use the pattern to quickly gear up for its own entry into the war, resulting in the M1917, the "American Enfield". This resulted in the interesting situation where the Americans mostly joined the war with a rifle that wasn't their standard, thanks to the already established production lines.

Further revisions led to the adoption of the Mk III, the best known variant of the SMLE in early 1907. These sported a proper charger bridge with integral guides for the chargers, providing much more stability, a simplified rear sight setup, as well as changes to the handguard and chamber, the latter to accommodate the new Mk VII ammunition with a conical bullet.
Had history taken another route, the SMLE Mk III might have have stayed a peacetime arm. In the early 1910s, the British were looking at the adoption of a new style of rifle, using a Mauser 1898 action to accommodate a smaller diameter, but very high speed bullet, .276 Enfield. The outbreak of hostilities in 1914 proved to be the saviour of the SMLE as a mainline service rifle.
Although it proved to be a worthy adversary in the trenches of the Western Front thanks to its shorter length and rear-locking action that kept most debris out of the receiver, features such as the magazine cutoff, the long range dial and the windage adjustment made it too complicated to produce.
Thus, in order to keep up with the staggering loss of material on the front, the Mk III* was introduced, removing the aforementioned features, as well as changing the cocking piece to an easier to produce shape.

As these changes were not implemented universally or simultaneously, SMLEs can be found with a variety of combinations of those features. Additionally, the magazine cut-off was re-introduced after the war, before finally being abandoned in the 1930s.
Some rifles were also outfit with grenade launchers. Due to the stocks being prone to bursting while doing so, these were often reinforced with copper wires to keep them from doing so.

Despite being on its way out in early 1914, the SMLE proved itself during and saw production in excess of five million pieces. The model would remain in use with Britain during the Second World War (called Rifle No. 1 Mk III or III* since 1926) as well, despite efforts to replace it with the updated Rifle, No. 4 Mk I starting from 1941.
Other nations of the Commonwealth would use the SMLE even longer, with Indian production extending into the 1980s, updated for the standard NATO 7.62x51mm by then.