The Civil War era marked the beginning of a rapid transition from the cap & ball system to metallic cartridges. The cap & ball revolvers had to be loaded with loose powder and lead ball, sometimes packed together in a rather fragile paper "cartridge", adding a percussion cap to the nipple at the rear of each chamber. The durable, weather resistant, and much faster loading self-contained metallic cartridges (predecessors of the ammo used in handguns today) were an obvious advantage. Many percussion revolvers were "converted" by various systems to fire the new metallic cartridges; some at the various factories, some by gunsmiths or frontier blacksmiths. In addition, some of the guns we call "cartridge conversions" today were actually originally assembled by the factories as cartridge revolvers, with design changes to allow obsolete percussion revolver parts still in inventory to be used up in a more economically viable product.

In the boom years in the American West immediately following the Civil War, it’s safe to say that these 1870’s produced cartridge conversions played a significant role. Through the 1870’s & into the 1880’s, they were probably much more readily available than revolvers originally designed for cartridges, and doubtless saw wide usage.

Excellent introductory material to Colt cartridge conversion revolvers, along with may other makes, can be found in various chapters of Flayderman's Guide to Antique American Firearms and their Values.

The definitive work on these fascinating and historically significant revolvers is the somewhat misleadingly named "A Study of Colt Conversions and Other Percussion Revolvers", by the late Bruce McDowell. While this book is indeed the best treatment available on Colt Conversions, it is much more than that, offering information on most American made conversions which can be found no where else.

There is also an excellent specialized study of Colt Pocket Model "conversions" - Variations of Colt's New Model Police & Pocket Breechloading Pistols by Breslin, Pirie, & Price.  These authors are emphatic (and correct) in pointing out that the "conversion" label is inappropriate for these Colts, as many if not most were originally manufactured as cartridge revolvers, and not "converted" from anything.  Whether the more-accurate terminology of "Colt Breechloading Pistols" will catch on with collectors remains to be seen.