Thanks for the input guys.

I checked Numrich online and they have extractors for the large frame Martini. I need to call them to see if they are for the 450 or 303 caliber. If they are for the 450, I don't think I can use them.

The chamberings suggested are all fine. It's just that I have the reamer, brass, bullet molds, and dies for the 45-70 and the reamer and easy access to lots of 30-30 brass to form the 7mm-30 Waters. The 303 would probably be the easiest to fit to the action but bullet selection is much more limited and I have no 303 loading stuff.

I really would like to have the barrel measurements if anyone has them, or, alternatively, direct me to where they can be found.