One of the British lessons form the Boer War was that the distinction between infantry rifles and cavalry carbines was becoming obsolete. In 1902, they would initiate troop trials on a new short rifle pattern, intermediate in length between the old rifles and carbines, and intended to be issued universally to all troops. This would become the much-loved SMLE - Short, Magazine, Lee Enfield rifle - but first a few choices had to be made.
The 1902 trials rifles were a bit remarkable in being widely liked by the different troops that used them - only a few changes were to be made before formal adoption took place. However, there were two different patterns of the trials rifles, with different models of rear sight. The B pattern used a friction-locked range adjuster, which was found to migrate during firing (not good). The A pattern had a much more secure set of spring loaded locking notched, and would be chosen as the better of the two.
Despite a thousand of these rifles being produced for the trials, these two are the only known surviving examples. The remainder were converted in .22 caliber training guns around 1907, as their non-standard nature made them unsuitable for issue after the formal adoption of the SMLE MkI (later to be retroactively redesignated the Rifle No1 MkI.
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