Blacktail, What are your intentions with this Martini?
I have a BSA Martini heavy wall target in 22RF that was shot out so decided to modify it to something more useful. Turned it into a "Wildcat" 22/357 Maximum. This can easily be done by your gunsmith using a 223 Improved reamer and pushing it in the correct depth, obviously you need to change the extractor claw but thats about it unless the barrel needs replacing.
Bravo 27
A friend DOWNUNDER