Remington Model 1858 converted to fire metallic cartridges - these were found to be more durable than Colt’s new Open-Top because of their solid frame.
Percussion Colt Army Model 1860, adopted by the Union Army the Model 1860 like the Open-Top 1871-2, relied on a ‘wedge’ that held the barrel and frame together.
Colt 1873 Single Action Army, the Colt Open-Tops successor