The Carbine of Mr. James H. Merrill
During the Civil War, the 2-million man Union Army needed modern firearms and they needed them yesterday. Besides buying up German, British and French designs in Europe, they let it be known that they would take (just about) anything from domestic producers that had rifling .
They could fire relatively rapidly for a breechloading rifled musket
Thats when Baltimore gunsmith James Merrill came about with a design for a handy little .54-caliber breechloader (this in itself made it pretty sweet as almost everything else was a front-stuffer) that used a nice tilting-block action.
Although he had designed the gun before the war, nobody wanted it.
However in 1863 he hit pay-dirt and managed to get some 14,500 of various models produced and sold before the end of the war. In all about a dozen bluecoat regiments marched or rode off to war with Mr. Merrill’s little gun.
They are exceptionally rare today.

Here is a Merrril Second Model Carbine on exhibit at the Fort Morgan Museum, Gulf Shores, Alabama. You can tell its a 2nd model due to the fact that it doesnt have a patch box in the stock, which earlier editions did. Photo by Chris Eger but anyone can use it feel free!. Click to very much big up
a