"Just a little confused You can shoot a 45 long colt, But does it have to be BP or off the self shell's??"
Black powder, or "cowboy action loads" which are reduced power smokeless loads used for SASS competitions. Available lots of places. That's the "official" recommendation.
The truth of the matter is that if you shoot either a Pietta or Uberti frame, especially the topstrap-fitted Remington copies, you have a frame that is as strong as a modern handgun, and a new cylinder that is also as strong as a modern handgun. Used with *sensible* smokeless powder loads it will be safe. Basically "stock" .45 LC loads work, those being the ones that are sold for use with Colt SAA's and similar, using SAAMI guidelines. You do NOT want to shoot the maximum loads that are available for things like the Ruger Blackhawks, etc.
The Pietta Remington for sale in the "for sale" area of this forum would be an excellent choice for a cartridge conversion, BTW.
Willie
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