There never was a military ".38-200" round
There never was a military ".38-200" round. That designation was a Kynock one for their commercial version of the 200gr lead bulleted "Cartridge, S.A. Ball, Revolver, .380-in Mk I". The Mk I was made obsolescent in 1937 when the Mk II round of the same name was introduced with a 178 gr cupro-nickel jacketed bullet.
.38/200 designation
The British continued to use the .38/200 designation even though they changed to a different 178-grain bullet in 1938 and, during the war, went on to use American-made Smith & Wesson Victory models in .38 S&W as well as the Webley Mk IV .38/200
new foresights were issued to compensate
The Enfield No.2 Mk I was designed for use with the Cartridge S.A. Ball Revolver .380 inch Mk. I and Mk. Iz, a deviation of the .38 Smith & Wesson cartridge, also known as the .38/200. It had a 200 gr (13 g). unjacketed round-nose, lead bullet of .359 inch diameter that developed a muzzle velocity of 620–650 ft/s (190–200 m/s).
Just prior to the outbreak of the Second World War, British authorities became concerned that the soft unjacketed lead bullet used in the 380/200 might be considered as violating the Hague Convention of 1899 governing deforming or 'explosive bullets'. A new .38 loading was introduced for use in combat utilizing a 178-grain (11.5 g), gilding-metal-jacketed lead bullet; new foresights were issued to compensate for the new cartridge's ballistics and change to the point of aim.
The new cartridge was accepted into Commonwealth Service as "Cartridge, Pistol, .380 Mk IIz", firing a 178 - 180 grain (11.7 g) full metal jacket round-nose bullet. The 380/200 Mk I lead bullet cartridge was continued in service, originally restricted to training and marksmanship practice.
However, after the outbreak of war, supply exigencies forced British authorities to use both the 380/200 Mk I and the .380 Mk IIz loadings interchangeably in combat. U.S. ammunition manufacturers such as Winchester-Western supplied 380/200 Mk I cartridges to British forces throughout the war.
wrong ammo: .38 special will not work
the .38 special cartridge is not only longer than the cylinder will allow, but the brass is a smaller diameter than the .38/200 of the Enfield. the projectile is also .004 smaller in diameter and would not engage the rifling. .38/200 Enfield is the exact same as .38S&W which is available
380 Enfield No. 2 Revolver, by Mark Stamps and Ian Skennerton
book on this revolver
Publisher : Greenhill Books; Edition Unstated (January 1, 1993) Language : English Paperback : 126 pages ISBN-10 : 1853671398 ISBN-13 : 978-1853671395