"The "Air Service"'03 was developed during the First World War. The rifle was a standard Springfield M1903 with a specially made shortened stock and handguard, a modified rear sight, and a non-detachable 25-round extension magazine.
While there are other theories, the probable purpose for the rifle was as auxiliary armament for pilots forced down behind enemy lines. Since a pilot wouldn't be wearing a cartridge belt, the 25-round magazine provided a reasonable amount of ammunition "self-contained" in the rifle and ready for immediate use. Such a rifle would have been much more effective than the typical sidearms carried by aviators.
Ordnance Department documents refer to the rifles as being " ... stripped for Air Service," and 910 were manufactured by Springfield Armory in early- to mid- 1918. Serial numbers were in the 856,000 to 862,000 range.
Most of the "Air Service" rifles were sent to France late in the war, but none are believed to have been issued before the Armistice.
After the conclusion of World War I, virtually all of the rifles were either destroyed or converted to standard service rifle configuration.
Surviving original examples are extremely rare and valuable.
Interesting, between this and the Pederson device seems the military was quite keen on expanding the capabilities of the main infantry arm of the time. And all the while just south of the border a select fire detachable arm designed years ago went unnoticed. History is weird and facinating.