Hi, guys,
Bryce Canyon is correct. The original military meaning of a carbine is a short rifle firing the same ammunition as the standard rifle. Carbines were issued to Cavalry and Artillery units. The trapdoor and Krag carbines are examples. The WWII U.S. carbine used its own light cartridge, but it was not intended for a specific branch of the service.
The civilian definition of carbine usually also meant a short rifle, as in the Winchester carbines. Today, its meaning is whatever an advertiser says it is if the term will help sell guns.
Jim