The brass frame guns are more "look" than "shoot". They work, but the metal used is far less durable than steel. Less ductile too. Steel is actually rather elastic, which is why it is used for knives, guns, etc. Brass can be shaped into a gun or knife, but the best brass or bronze will be vastly inferior to a decent steel. Guns made of brass will have a fraction of the lifespan of a steel gun.
Keeping firmly in mind that the manufacturers of both the gun and converter will say "We really do not recommend that you do this", it is still a free country. No one will ticket you for putting these components together. The gun might survive, but it will have a very short lifespan. The end of that lifespan could be a quiet descent into inoperability, or a noisy abrupt one. Most cars do not blow up at redline or just over it, but it is unwise to ignore that clearly marked "do not exceed" line. I would buy a steel gun if I wanted to use a converter. I tend to shoot my guns quite a bit. My two Remingtons have over 3000 rounds through them, and are still in good shape. But I do not hot-rod them, either. If I want a "heavy load" BP revolver, I use a Ruger Old Army. It is built like a tank.
If I wanted to make a light BP cartridge load for my Ruger Vaqueros, (modern single action cartridge gun based on a Blackhawk) I would acquire some of the ".45 Cowboy Special" brass. It is essentially a .45 ACP case with a .45 Colt rim on it. Internal volume is the same as .45 ACP, so one can load modern powder in a modern .45 Colt gun, yet not experience the difficulties that arise from having a huge unfilled volume in a .45 Colt cartridge. One can load ones "cowboy" competition ammo using .45 ACP charges. These will use somewhat less powder that the equivalent Colt loads, and be more consistent to boot.
If you want to shoot reduced charge Blackpowder cartridges in Cowboy matches, the Cowboy Special brass is the way to go. The reduced volume allows a very light BP load, with no need for fillers, wads, etc. The resultant load contains a little over 1 cc of BP, to meet SASS rules for BP cartridges. My Lee powder measure kit has a chart of grain-equivalents to the volumetric Lee scoops. According to the Lee chart, 1 CC of FFg BP is equivalent to 14.7 grains. (BP varies in weight, so you have to measure by volume.) 15 grains is a very light charge. None of my cap and ball revolvers can use a charge that light without a wad or filler. The ram won't seat a bullet that deep.