Single Shot Breechloaders.
<p>ALLIN CONVERSION As muzzleloaders became dirty from firing, they became increasingly difficult to load. The bullet would frequently jam half way down the barrel and the soldier would attempt to fire the bullet out – an almost guaranteed way to damage the weapon of blow it up. Breech-loading weapons eliminated the hazards of multiple or stuck loads in the barrel.
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The experience of the Civil War had shown the need for such weapons, and at the close of the war the United States Government advertised for proposals for a breech-loading weapon - one that could be made by converting the vast supply of old muzzleloaders already on hand. Numerous proposals were submitted, trials were held, and the system that was selected was one submitted by Erskine S. Allin, Master Armorer of Springfield Armory.
Springfield Armory NHS, US NPS
<a rel="nofollow" class="external text" href="https://www.nps.gov/spar/learn/historyculture/images/case_19.jpg">Springfield Armory National Historic Site (U.S. National Park Service Official Web-site)</a> (<a rel="nofollow" class="external text" href="https://www.nps.gov/spar/learn/historyculture/evolution-of-the-breechloader.htm">link</a>)