The 38 Super is a higher velocity loading of the 38 Auto (ACP) and was introduced during the late 1920’s, about 27 years after the introduction of the 9mm Luger. During the early years and up to the end of WW2, the 9mm Luger was not well known in the US. It was only after the War that soldiers brought back captured 9mm’s that it started to take off. Before that the 38 Special and the 45 ACP were the handguns that American law enforcement relied on, although there were parts of law enforcement that felt that the penetration abilities of these were lacking, especially against criminal elements wearing light body armor as crime steadily spiked during the depression years. Colt saw this opportunity and chambered a higher-powered version of the 38 Automatic in their Model 1911 guns. They were successful initially, until the introduction of the 357 Magnum in 1935, which relegated the 38 Super to the beginning of its decline. On the 4th of April 1949 NATO was formed and most members adopted the 9mm Luger as their standard side-arm, although the US still hung on to the 45 ACP. In 1967 the Illinois State Police became the first major law enforcement agency to adopt the 9mm and most others followed not long after that. The final decline was in 1985 when the US adopted the 9mm Luger in their Beretta M9’s.
The 38 Super achieved a resurgence in the late 80’s when it was adopted for US Practical Shooting and IPSC competition shooting as it allowed a 38cal load to be loaded hot enough to make major power factor (Power Factor is the weight of the bullet in grains multiplied by the velocity in feet per second, divided by 1,000). This gave competition shooters an advantage in Open class as they had a gun that was more controlled than the 45’s. Most US loadings of the 38 Super utilised nickel plated cased to distinguish them so they are not used in lesser strength 38 ACP guns. (Erlmeier, Brandt Ref. 370)
Above is a rare 38 Super Auto US Army contract. The fascinating history of this gun can be found HERE