DD-Ret - didn't some of those little Martini's get re-barreled and chambered for the 5.54x50mm - or whatever that little .22 cak, long case was.
This made me think the .375 on a .30/30 case (.375 Winchester) would work as the ones I necked up are only 2" long, opposed to the almost 2.1" for the .38/55.