Everyone, please correct any of my errors as I'm sure I made a bunch of them and oversimplified the whole explanation!
I'm running completely from memory but I don't see any errors. I agree though and really don't think an in-depth discussion of all the finest details is really necessary.
I can add some stuff though.
As said, the type of conversion is not related to the model. The Richards Type I and Type II were only applied to the 1860. Only the later Richards-Mason was applied to the 1851.
Both Richards conversions utilized the percussion barrel. I think this makes them the best looking of the bunch. The Type I had the floating firing pin in the conversion ring with the flat-faced hammer. Also the rear sight was in the conversion ring.
The Type II had the rear sight notch in the hammer, as well as the firing pin. This was an easier, more cost effective conversion to produce. There are some other minor differences in parts like ejectors and the loading gate spring but you get the gist of it.
Then the Open Top came along in the 1871-1872 period and was the first purpose-built cartridge sixgun. Not a conversion. It utilized an all-new frame and barrel. While it resembled the 1860 and its conversions in appearance, it was indeed a dedicated cartridge gun. The Army rejected it in 1872 in favor of a solid frame and .45 caliber and William Mason designed the Single Action Army in a matter of months, offering it to the Army in late 1872. The rest is history.
As Colt ran out of percussion barrels, both Charles Richards and William Mason went back to the drawing board and began utilizing the Open Top's S-lug barrel on the 1860 conversion. Which became known as the Richards-Mason conversion. This is the only conversion applied to the 1851 model.
If you're really interested in this stuff, I'd highly suggest Dennis Adler's book on the subject,
Metallic Cartridge Conversions. He also covers them in his other books, though to a lesser extent,
Colt Single Action: From Patersons to Peacemakers and
Guns of the American West. I'd suggest the first one first, because it is out of print and subject to limited availability. His stuff is excellent and I'll probably buy every gun book he writes. I even got the leatherbound edition of
Guns of the American West from Easton Press.
I really think these new replicas are the best thing since sliced bread. I blame Tom Selleck and his movies for much of it. I'd love to eventually have at least one of each variation. I've really got the hots for an 1860 Type I with a 5½" barrel, antiqued finish and heavily aged ivory stocks. Which is a scratch I may decide to itch by modifying my Richards Type II. I've also been lusting after the little 1851 Richards-Mason with the 4¾" barrel. I'd like to also eventually have Bob Millington build me one out of a genuine Colt.
