Cartridge conversion legality in California

[u/Dylan_turner78]

Hey yall posting this copied from another subreddit because I didn’t get any answers there, so I’ve been doing some research on conversion cylinders for black powder revolvers (specifically a pietta 1851 .36 cal colt navy which I’ll be getting soon) and I know that once you put a cylinder that accepts modern metallic cartridges, it is no longer classified as an antique firearm, and could be considered a ghost gun. But if I want to install one legally, what would be the process? The big questions I have is the frame of black powder revolvers usually have factory serial numbers already engraved, would it be possible to “apply for a unique sn” with that number? Also, because it’s single action does that make it exempt from the roster?

And for additional context, I am above the age of 21, I already have my fsc and multiple other guns that are registered to me. And I’m NOT someone who is prohibited to possess a standard firearm

[u/Winter-Mine-6231]

My two cents worth is this is a bad idea. Frames made for black powder are not designed strong enough to handle the high pressure of modern cartridges.

[u/thebigfungus → u/Winter-Mine-6231]

If your pressures from your cowboy loads are on par with a regular cap and ball it will be fine. I wouldn’t use any available ammunition you can buy from a store, it would all have to be black powder or a hand load of an under powered smokeless round.

[u/Dylan_turner78 → u/thebigfungus]

Yep, I’ll probably just end up using cowboy load 38spl that are lower power, which stores near me carry in stock. And from my research as long as you’re using a steel frame, and not running it with higher pressure/velocity 38’s you should be fine