Covered by a disc made of greased felt, the projectile was inserted in the barrel after it was tilted up by a lever, followed by the case, and (like the concurrent muzzleloaders, such as the Springfield) were ignited by percussion cap, which was placed on the bolt face.

The brass cases had a paper patch in the base, to prevent powder seepage and still allow the cap to fire the round.

After the presentation, the Ordnance Department ordered the modification of 5,000 Gallager carbines with a cap lock to the new version.

In 1870, Schuyler, Hartley and Graham of New York City purchased from the Government 2,500 of the Gallagers chambered for the Spencer cartridge at a cost of $12.25 each and shipped them to France for the Franco-Prussian War.

The Gallager carbines, after the warfare in the 19th century, were modified in various variants for private use by shooters, due to their solid workmanship.

[2] Erma Werke in Germany manufactured a Gallager carbine replica in .54 caliber with barrels sourced from Lothar Walter.