Proprietary brass cartridge for the Burnside Carbine, one of the most-issued Civil War cavalry weapons; a transitional design with a hole in the base for the percussion cap.
Type: Rimfire
Introduced: 1857, United States
Parent case: Proprietary brass (transitional)
Standardization: Proprietary
Bullet diameter: 0.54" (13.72 mm)
Rim type: Rimmed
Primer: Rimfire
Production status: Discontinued
Also known as: .54 Burnside Carbine · Burnside carbine cartridge · .54 Burnside RF
History: Developed in 1857 by Ambrose Burnside for his Burnside Carbine, this is a transitional cartridge — the tapered brass case held the bullet and powder, but required a separate percussion cap at the base rather than being fully self-contained. Over 55,000 Burnside Carbines were issued to Union cavalry during the Civil War, making this one of the more historically significant 19th-century cartridges.