Craig, I'd have to respectfully disagree- even Uberti calls it the "Open Top conversion" and "not a conversion" on their website- it used the 1851/60 frame and lockwork
"designed from the start as cartridge" is a real stretch- all they did was got rid of the loading lever, didn't use a conversion ring on the frame, and used a barrel with solid lug, without a cutout for loading powder/ball from the front- the entire back half of the gun is the same
that's like saying a Chevy is a whole new car, nothing like a Pontiac- when they both use the same engine, transmission, frame, tires, wheels, brakes- just the badge and seats are different- who falls for that line ? Anyone with technical expertise, sees the identical parts used, and realizes it's the same car.
I don't call that a whole new design, I call that a rework of an old design, or upgrade
it's obvious the Open Top was an 1851/60/61 pattern with a long cylinder- that's why an Open Top cylinder worked in my 1851 cap/ball gun- calling it an "all new design" and "not a conversion" was splitting hairs, semantics, and parsing words.
The entire back half of the gun is an 1851/60/61 pattern. The grips, lockwork, grip frame, bolt, screws, trigger guard, wedge, springs all interchange with cap/ball, they are the same parts. It used same same exact ejector rod/housing assembly as the 1860 Richards-Mason cartridge conversion.
heck, for that matter, the Peacemaker is only a reworked 1851 too, it uses the same grips and many other identical parts- if you took a bridgeport/saw/grinder to a Peacemaker you could easily whittle an 1851 out of it- just cut off the topstrap and front frame, and change the arbor/barrel.
when they say it wasn't a "conversion", they say that tongue in cheek to the uninformed- because 95% of the Open Top was a cap/ball design
http://www.ubertireplicas.com/revolver-1872opentop.php
The 1872 Colt Open Top Revolvers were produced simultanneously with the Richards and Richards-Mason Conversion. Between February 1872 until June 1873, a total of 7,000 pieces were produced. This Colt revolver is not a conversion but was produced for metallic cartridfges: the barrel, cylinder and frame were made intentionally, whereas parts such as the grip assembly and the internal components were adapted from the Navy '51 and the Army '60. Production stopped abruptly when the Single Action was introduced.