It is not the receiver that takes the pressure from the cartridge, but the cylinder, and both R&D and Kirst are modern, smokeless proofed steel. The only caveat is the thin walls of the Remington cylinder due to the "bolt circle" and the overall diameter. Standard SAAMI loads are safe.
Recoil-wise, the Remington has a flat faced breech and the cylinder as well, so they are easier on the parts under recoil than the Colt, as far as battering the breech face. The cap & ball barrels tend to be soft (particularly the Pietta) so the forcing cone takes more of a beating. The cartridge bullet is both heavier and harder than the round ball, but I haven't seen any stretching of the frame. For Colt types, the conversions are harder on the cylinder arbor threads and the wedge, but they seem to hold up pretty well.
There are two Uberti frames, the cast one, as used for years for the cap & Ball, and the new, slightly larger frame, made of forged steel used for the "Conversion" This new, larger frame is also available for the cap & ball, and has a larger radius to the center of the bore, therefore, thicker walls. A Kirst or R&D cylinder would have to match that new frame, and I haven't seen any reference to it. The Uberti factory conversion is a six-shot revolver, so the chamber spacing has to have been increased.
The R&D or Kirst cylinders are better made and of higher grade steel than the entirety of the Pietta or Uberti revolver, and that makes the revolver the throw-away part, when worn out...... Hence the high price of the cylinder, beyond being made in the USA.
The Uberti factory conversion is made of higher grade steel (in all parts) than the cap & ball they have made in the past.
