It is a black powder cartridge, based on the .577 caliber cartridge used in the Snider rifle.

The early version of the cartridge used a Boxer-style casing, based on the .577 Boxer rifle cartridge used in the Snider conversion. The projectile used was a round lead ball. This casing came in different lengths, ranging from .078 to 1.21 inches (19.8 to 30.73mm). The overall length ranged up to 1.42 inches (36.06mm). The rim would sometimes back up against the revolver's recoil plate on firing, causing a jam. Tranter's revolver design incorporated a separate backplate at the rear of the cylinder, which was it keyed to and rotated with.

When solid drawn brass cases were introduced, Eley Brothers began manufacturing the cartridge with this type of casing while still also offering the original Boxer construction. The drawn brass cartridge has a typical case length of .80 inches with a 1.22 inch overall length, made with both flat- and round-nosed bullets. The bullet weight ranges from 19.7 grams (304.01 grains) to 31.7 grams (489.7 grains).

Because the cartridge casings were based on the .577 rifle cartridges, headstamps are sometimes (rarely) seen that refer to the rifle case used in the manufacture of the revolver cartridges. For instance, some cases were based on the .577/450 cartridge as indicated by the headstamp.

Eley Brothers had also manufactured shot loads with tied-nose and folded nose paper containers. Folded nose shot rounds were made in a variety of lengths, three of which being 1.17, 1.25, and 1.34 inches.