Smaller, lighter versions of the Martini-Henry were created to train young military cadets. These weapons, often referred to as Martini Cadets, are similar in appearance to Mark IV's, but are much smaller and lighter. Many also feature August Francotte's improved action design, whereby the entire "guts" of the action can be removed by removing a single pin or screw. Government issue Cadets were originally in .297/230 Morris (Short and Long) and .310 Cadet (a.k.a. .310 Greener). These cartridges, like the .450 Martini-Henry, have fallen into obsolescence, and are nearly impossible to find in the US. Thus, conversion of these rifles to readily available rimmed cartridge calibers such as .357 Magnum, 32-20 WCF, 218 Bee, and 22 Hornet is very popular. The cadet's action is extremely strong. According to a 1955 data circular, the cadet action was tested with proof loads generating up to 60,000 PSI!!! Alas, the adoption of the Lee-Metford Magazine Rifle in 1888 would lead to the phasing out of the single-shot Martinis. Nonetheless, the Martini survived for many more years as a Home-Guard and second class weapon of the British and Colonial Armies.