Howdy
I have a very old EuroArms 1858 Remmie, as well as a pretty new Stainless Uberti Remmie. I have R&D cylinders for both of them.
Anybody who does not think brass frames stretch is welcome to come see my old Navy Arms brass framed 44 Cal 'Navy' that I bought in 1968. It is now a wall hanger because too many heavy charges stretched the frame and the barrel now points up high enough that it shoots about 12" above point of aim at CAS distances. Unfortunately, back in 1968 nobody warned us against heavy loads in brass framed revolvers, so I kept loading it with 30 grain charges until I finally noticed I couldn't hit anything with it anymore.
With a 45 Colt cartridge and a 200 or 250 grain bullet in a conversion cylinder, the frame will be subjected to more pounding from recoil than a 148 grain or so 44 cal round ball can ever generate. If you want to shoot a conversion, spend the extra money on the steel frame.
If you are on a budget, you may want to rethink your strategy. Although the raw price of a C&B revolver is quite attractive, you have to spend over $200 each for the conversion cylinders, no matter which brand. With me, I bought my old EuroArms Remmie back around 1975, so dropping $200 on a conversion cylinder for it a few years ago did not hurt very much. Later on I came across the Stainless Uberti used at a gunshow at a very attractive price, including the conversion cylinder. Couldn't pass it up. But once you are done buying a C&B revolver brand new, and a brand new conversion cylinder for it, you have spent just about as much money as you will on most other cartridge revolvers made in Italy.
Don't get me wrong, Remmies with cartridge conversions are fun. But they ain't cheap.
I have no experience with Pietta, I cannot speak about them. I am continually dissapointed with Uberti quality, and the Stainless Remmie did not let me down. It shoots fine, but there are a couple of minor manufacturing defects in it that would not bother most, but bother me. The hammer never drops straight down into the hammer slot in the frame. It always grazes the side of the frame as it falls. When I gave it to my smith to see if he could do anything about it he told me the hole for the hammer pivot screw was cocked slightly, causing the hammer to fall slightly to one side. Rather than weld up and redrill the hole, he relieved one side of the hammer so that the interference was lessened, but not completely eliminated.
Conversion cylinders can never be truly 100% 'drop in'. There are always manufacturing tolerances involved in making the revolvers so that one is never completely identical to another. To partially overcome this, conversion cylinders have to actually be manufactured to tighter tollerances than the guns they fit into. That is one reason they are so expensive.
I have no experience with the Kirst product.
R&D makes 3 generic versions, one for Ubertis, one for Piettas, and one for the Ruger Old Army. R&D does a very good job of making their cylinders as truly drop in as possible. Even so, every once in a while a Remmie will be encountered that needs a little bit of TLC to make a conversion cylinder drop in and function correctly. Case in point is my old EuroArms Remmie. Neither a standard Uberti or Pietta cylinder would fit it. I sent it off to Taylors to have them custom fit a cylinder to it. Taylors is the official distributor for R&D cylinders. I might add that custom fitting is a service that Taylors performs
for free for R&D cylinders. They custom fit a 'pietta' cylinder to the old Remmie and it works fine.
The best books I know about for getting started shooting Black Powder in revolvers are either Shooting Colt Single Actions, or Shooting Sixguns of the Old West, both written by Mike Venturino. The Colt book was my own primer for getting started with BP cartridges, I already knew about C&B, except for not loading heavy charges.
http://www.ycsi.net/users/mlventurino/