It should be a #11 cap.
The correct size of the bullet that fits the rifle.
Caliber
The 1863 Springfield rifle typically uses a .58 caliber musket cap. Specifically, it is designed to use a percussion cap that fits the nipple of the rifle, which is usually a standard size used for .58 caliber muzzle-loading firearms. When selecting caps, it's important to choose high-quality options for reliable ignition.
Generally refers to size of projectile.
Caliber
a rifle cap.
Caliber
caliber
Are you asking about caliber or the actual size of the rifle?
Caliber is the size designation for rifle and handgun bullets. Guage is the size designation for shotgun rounds.
Caliber
Caliber