The Martini Enfield is the lge martini henry action and needs a rimmed case to extract.
I had a .358 barrel and wanted to do something which could push a heavy bullet fairly quickly without high chamber pressures.
I settled on the .35 Whelen and looked for a case to convert. The German 9.3x74R RWS round is ideal. So I got 60 and shortened them to 64.5mm then necked them down and outside neck turned them. They work very well.
The other case there is a 6.5x54R that is made from a 7.62x54 Russian case, sized and fire formed to the 6.5x55 Swedish.
It is the spare barrel for the Martini and is a great caliber.
The rifle and both barrels will go with me to New Zealand soon for deer and pig hunting. Im leaving the rifle there as it doesn't have much practical use here in WA. I mostly use a .223 and .243 here on foxes, roos and rabbits.
Im building a bolt action 27" 6.5x55 Swedish for long range.
Good luck with the hunt for a scope and happy hunting