the cartridge is very close to the .416 JDJ round wildcat here in the USA. This is the .444 marlin necked to the .416. A bit more capacity than the .303 case.
I am making a case with .375 bullet on the .303 case for my 2 1/4 " version of the .375 express in a martini henry. 250 - 300 grain bullets. The 250 should be pushing 2000 fps.
Nice hog and deer load.